Incontinence therapy

ABSTRACT

Techniques for managing urinary or fecal incontinence include delivering a first type of therapy to generate a first physiological response and, upon detecting a trigger event, delivering a second type of therapy to generate a second physiological response. The first type of therapy can be delivered on a substantially regular basis, while the second type of therapy is delivered as needed to provide an additional boost of therapy. The trigger event for activating the delivery of the second type of therapy may include input from a sensor that indicates a bladder condition, patient activity level or patient posture, or patient input. In some examples, the therapy is stimulation therapy.

This application is a U.S. National Stage filing under 35 U.S.C. 371 ofcopending PCT Application Serial No. PCT/US2010/030559, filed Apr. 9,2010, which claims priority to U.S. Provisional Application Nos.61/172,584, filed Apr. 24, 2009, and 61/183,019, filed Jun. 1, 2009, thedisclosures of each of the above which are incorporated by reference asif re-written herein in their entirety.

TECHNICAL FIELD

The disclosure relates to implantable medical devices and, moreparticularly, medical devices for the treatment of urinary or fecalincontinence.

BACKGROUND

Urinary incontinence, or an inability to control urinary function, is aproblem that afflicts people of all ages, genders, and races. Variousmuscles, nerves, organs and conduits within the pelvic floor cooperateto collect, store and release urine. A variety of disorders maycompromise urinary tract performance, and contribute to incontinence.Many of the disorders may be associated with aging, injury or illness.

In some cases, urinary incontinence can be attributed to impropersphincter function, either in the internal urinary sphincter or externalurinary sphincter. For example, aging can often result in weakenedsphincter muscles, which causes incontinence. Some patients may alsosuffer from nerve disorders that prevent proper triggering and operationof the bladder, sphincter muscles or nerve disorders that lead tooveractive bladder activities. Nerves running though the pelvic floorstimulate contractility in the sphincter. An improper communicationbetween the nervous system and the urinary sphincter can result inurinary incontinence.

SUMMARY

Techniques for managing urinary or fecal incontinence are described.According to one example, an implantable medical device (IMD) deliversfirst stimulation therapy to generate a first physiological responsethat helps prevent the occurrence of an involuntary voiding event and asecond stimulation therapy to generate a second physiological responsethat helps prevent the occurrence of an involuntary voiding event. Thefirst and second physiological responses are different, and in someexamples, involve the activation of different muscles.

The IMD delivers the first stimulation therapy on a regular basis, e.g.,to reduce bladder contractions, and, when triggered, delivers the secondstimulation therapy, e.g., to promote closure of a urinary or analsphincter. The IMD delivers the second stimulation therapy upon thedetection of a patient parameter indicative of a high probability thatan involuntary voiding event will occur or based on patient input. Thesecond stimulation therapy provides a safeguard in addition to theprimary incontinence therapy (i.e., the first stimulation therapy)against the occurrence of an involuntary voiding event. Thus, the secondstimulation therapy provides an increased protection against theoccurrence of involuntary voiding events when needed or desired.

In one aspect, the disclosure is directed to a method comprisingdelivering, with a medical device, a first electrical stimulationtherapy to a patient to generate a first physiological effect, receivinginput from the patient or a sensor while the medical device isdelivering the first electrical stimulation therapy, and delivering,with a second medical device, a second electrical stimulation therapy tothe patient to generate a second physiological effect that is differentthan the first physiological effect based on the input from the patientor the sensor, wherein the first and second electrical stimulationtherapies are configured to manage one of urinary incontinence or fecalincontinence. The first and second electrical stimulation therapies canbe delivered at substantially the same time or at different times, whichdo not overlap.

In another aspect, the disclosure is directed to a method comprisingcontrolling, with a processor, a medical device to deliver a firstelectrical stimulation therapy to a patient to generate a firstphysiological effect, receiving input from the patient or a sensor, andcontrolling, with the processor, the medical device to deliver a secondelectrical stimulation therapy to the patient to generate a secondphysiological effect that is different than the first physiologicaleffect based on the input from the patient or the sensor, wherein thefirst and second electrical stimulation therapies are configured tomanage one of urinary incontinence or fecal incontinence.

In another aspect, the disclosure is directed to a medical systemcomprising a therapy delivery module that generates and delivers a firstelectrical stimulation therapy to a patient to generate a firstphysiological effect and a second electrical stimulation therapy to thepatient to generate a second physiological effect that is different thanthe first physiological effect, and a processor that controls thetherapy delivery module to deliver the second stimulation therapy basedon received input, wherein the first and second electrical stimulationtherapies are configured to manage one of urinary incontinence or fecalincontinence.

In another aspect, the disclosure is directed to a medical systemcomprising means for delivering a first electrical stimulation therapyto a patient to generate a first physiological effect, means forreceiving input from the patient or a sensor, and means for delivering asecond electrical stimulation therapy to the patient to generate asecond physiological effect that is different than the firstphysiological effect based on the input from the patient or the sensor,wherein the first and second electrical stimulation therapies areconfigured to manage one of urinary incontinence or fecal incontinence.

In another aspect, the disclosure is directed to a computer-readablemedium containing instructions. The instructions cause a programmableprocessor to control a therapy delivery module (e.g., of a medicaldevice) to deliver a first electrical stimulation therapy to a patientto generate a first physiological effect and deliver a second electricalstimulation therapy to the patient to generate a second physiologicaleffect that is different than the first physiological effect based onreceived input (e.g., patient input or input from a sensor indicative ofpatient activity, posture or bladder condition). The first and secondelectrical stimulation therapies are configured to manage one of urinaryincontinence or fecal incontinence.

In another aspect, the disclosure is directed to an article ofmanufacture comprising a computer-readable storage medium comprisinginstructions. The instructions cause a programmable processor to performany part of the techniques described herein. The instructions may be,for example, software instructions, such as those used to define asoftware or computer program. The computer-readable medium may be acomputer-readable storage medium such as a storage device (e.g., a diskdrive, or an optical drive), memory (e.g., a Flash memory, random accessmemory or RAM) or any other type of volatile or non-volatile memory thatstores instructions (e.g., in the form of a computer program or otherexecutable) to cause a programmable processor to perform the techniquesdescribed herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example therapy systemthat delivers a first stimulation therapy to a patient and, whentriggered, a second stimulation therapy to manage urinary incontinence.

FIG. 2 is a conceptual diagram illustrating another example therapysystem that delivers a first stimulation therapy and, when triggered, asecond stimulation therapy to a patient to manage urinary incontinence.

FIG. 3 is a block diagram illustrating an example configuration of theimplantable medical device (IMD) of the systems shown in FIGS. 1 and 2.

FIG. 4 is a block diagram illustrating an example configuration of theexternal programmer of the systems shown in FIGS. 1 and 2.

FIGS. 5-10 are flow diagrams illustrating example techniques ofdelivering first stimulation therapy and, when triggered, a secondstimulation therapy to a patient to manage urinary incontinence.

FIGS. 11, 12, 13A-13C, and 14A-14C illustrate example stimulationsignals that may be delivered as part of a second stimulation therapy.

FIG. 15 illustrates an example prestimulus that is delivered prior tothe second stimulation therapy.

DETAILED DESCRIPTION

Urinary incontinence refers to a condition of involuntary loss of urine,and may include urge urinary incontinence, stress incontinence, or bothstress and urge incontinence, which may be referred to as mixed urinaryincontinence. As used in this disclosure, the term “urinaryincontinence” includes disorders in which urination occurs when notdesired, such as stress or urge incontinence, and disorders in whichurination does not occur as desired, such as urinary retention disorder.Stress or urge incontinence may also be referred to as overactivebladder or as leading to overactive bladder activities. Althoughtherapies for treating urinary incontinence, such as electricalstimulation to the bladder for fluid retention, are effective,involuntary events may still occur.

One type of therapy for treating urinary incontinence includes deliveryof electrical stimulation. For example, delivery of electricalstimulation from an implantable medical device to nerves in the pelvicfloor, such as the sacral nerve, pudendal nerve, dorsal genital nerve,or branches of any of the aforementioned nerves may provide an effectivetherapy for urinary incontinence. Electrical stimulation of the sacralnerve may modulate afferent nerve activities to restore urinaryfunction. In addition, electrical stimulation of the nerves innervatingpelvic floor muscles may strengthen pelvic floor muscle and promoteurinary continence.

Techniques described in this disclosure include delivering a firstelectrical stimulation therapy to a patient to generate a firstphysiological effect to manage urinary or fecal incontinence and, whentriggered, delivering a second electrical stimulation therapy togenerate a second physiological effect that further helps to prevent anoccurrence of an involuntary urinary or fecal voiding event. The secondstimulation therapy may, therefore, provide an additional safeguardagainst the occurrence of an involuntary voiding event in situations inwhich the involuntary voiding event may be likely to occur. In somecases, only the second stimulation therapy is delivered to the patientto manage urinary or fecal incontinence.

The first stimulation therapy may be a chronic (e.g., non-temporary)therapy delivered to the patient to control urinary or fecalincontinence. In general, the first electrical stimulation therapy isdelivered on a substantially regular basis to manage patientincontinence. In some examples, the first electrical stimulation isdelivered to a patient in an open loop, i.e., without the use of anexternal feedback mechanism such as a sensor. However, in some cases, asensor signal or patient input may be used to adjust the stimulationparameters of the first stimulation therapy.

The second electrical stimulation therapy may be referred to as atemporary stimulation therapy because the second electrical stimulationtherapy is delivered for a predetermined period of time (duration oftime), rather than on a regular basis. In some examples, thepredetermined period of time may be controlled by the patient. Inaddition, the second stimulation therapy may be referred to asfunctional electrical stimulation because the second electricalstimulation therapy results in a movement of muscles of the patient thatprovides a specific functional result. For example, the secondstimulation therapy may generate a contraction of the urinary or analsphincter of a patient. The second stimulation therapy may also bereferred to as “boost” therapy because of the additional “boost” oftherapy compared to the first stimulation therapy provided by the secondelectrical stimulation. In examples described herein, the secondstimulation therapy is delivered to the patient in a closed loop mannerbecause the initiation of the delivery of the second stimulation therapyis dependent upon an occurrence of a trigger event, as described infurther detail below.

In some examples, an implantable medical device (IMD) delivers the firstand second stimulation according to different sets of stimulationparameters and/or to different target tissue sites within the patient.However, in some examples, the first and second stimulation therapiesare delivered to the same nerve (e.g., the sacral or pudendal nerve).

In some examples, the IMD may deliver the first stimulation therapy to asacral nerve to improve pelvic floor muscle tone or to an afferent fiberof the sacral or pudendal nerves to inhibit bladder contractions, e.g.,to relax the bladder. In addition, in some examples, the firststimulation therapy helps close or maintain internal urinary sphincterclosure or urethral tone. The IMD may deliver the second stimulationtherapy to a hypogastric nerve, a pudendal nerve, a dorsal penile nervein a male patient, a dorsal clitoral nerve in a female patient, or tothe external urinary sphincter or any combination thereof to promotecontraction of the internal urinary sphincter, or promote externalurinary sphincter closure or periurethral muscle contraction. In someexamples, the second stimulation therapy may be viewed as a short-termboost to the effectiveness of the first stimulation therapy.

The second stimulation therapy may be triggered when a patient conditionindicative of an imminent involuntary voiding event or an increase in apossibility that the involuntary voiding event will occur is detected.The patient condition may be, for example, a bladder contraction. Thebladder contraction may be detected via any suitable sensing mechanismor under the control of the patient. For example, the IMD may detectbladder contraction based on bladder impedance, bladder pressure,pudendal or sacral afferent nerve signals, external urinary sphincter oranal sphincter electromyogram (EMG), motion sensor signals (e.g.,accelerometer signals), or any combination thereof. Instead of or inaddition to a bladder contraction, the patient condition may be anabnormal detrusor muscle activity.

In other examples, the trigger event for activating the delivery of thesecond stimulation therapy may be patient input. In some examplesdescribed herein, the patient may use a medical device programmer oranother input mechanism to trigger the IMD to deliver the secondstimulation therapy. In some examples, the patient may also use theprogrammer to manually abort the delivery of the second stimulationtherapy. In such examples, the IMD may wirelessly communicate with theprogrammer to alert that patient of prospective delivery of the secondelectrical stimulation. In additional examples, the patient may use theprogrammer to inhibit second electrical stimulation therapy duringvoluntary voiding events.

Although the techniques are primarily described in this disclosure formanaging urinary incontinence, the techniques may also be applied tomanage fecal incontinence. In fecal incontinence examples, the IMDdelivers the second stimulation therapy when patient input is received,when a patient parameter indicative of an imminent fecal incontinenceevent is detected or when a patient parameter indicative of an increasedprobability of an occurrence of a fecal incontinence event is detected(e.g., an increased patient activity level). The patient parameter mayinclude, for example, contraction of the anal sphincter, patientactivity level or patient posture state. The IMD may use any suitablesensing mechanism to detect contraction of the anal sphincter, such as apressure sensor or an EMG sensor.

FIG. 1 is a conceptual diagram illustrating an example therapy system 10that delivers a first electrical stimulation therapy to generate a firstphysiological response of patient 14 to manage a urinary continencedisorder of patient 14, and, when triggered, a second electricalstimulation therapy to generate a second physiological response ofpatient 14. The delivery of the second stimulation therapy providesimproved protection against the occurrence of involuntary voidingevents. Therapy system 10 provides the first and second therapies togenerate respective physiological responses in the form of electricalstimulation. In other examples, therapy system 10 may be configured toprovide at least one of the first or second therapies to mange urinaryincontinence by delivering a therapeutic agent to patient 14.

Therapy system 10 includes an implantable medical device (IMD) 16, whichis coupled to leads 18, 20, and 28, sensor 22, and external programmer24. IMD 16 generally operates as a therapy device that deliverselectrical stimulation to, for example, a pelvic floor nerve, a pelvicfloor muscle, the urinary sphincter, the anal sphincter, or other pelvicfloor targets. Pelvic floor nerves include peripheral nerves such assacral nerves, pudendal nerves and associated branches, and dorsalgenital nerves. IMD 16 provides electrical stimulation therapy topatient 14 by generating and delivering a programmable electricalstimulation signal (e.g., in the form of electrical pulses) to a targettherapy site by lead 28 and, more particularly, via electrodes 29A-29D(collectively referred to as “electrodes 29”) disposed proximate to adistal end of lead 28.

IMD 16 delivers the first stimulation therapy periodically over anextended period of time, e.g., chronic stimulation, and automaticallydelivers the second stimulation therapy within that period of time andin response to a trigger event. The second stimulation therapy isdelivered for a predetermined duration of time, referred to herein as atherapy period. In other examples, IMD 16 delivers the secondstimulation therapy for a period of time controlled by the patient. Thefirst and second stimulation therapies may be delivered at substantiallythe same time, during overlapping time slots, or in different timeslots, such that IMD 16 only delivers one type of stimulation therapy ata time. In examples in which IMD 16 delivers one type of stimulationtherapy at a time, IMD 16 may deliver the first stimulation therapy,and, when triggered, deactivate delivery of the first stimulationtherapy and activate delivery of the second stimulation therapy. Afterthe second stimulation therapy period, IMD 16 may revert back todelivering the first stimulation therapy until another trigger event foractivating the delivery of the second stimulation therapy is detected.

A trigger event for activating the delivery of the second stimulationtherapy may be detected based on sensor or patient input. As oneexample, IMD 16 may sense a bladder contraction that triggers IMD 16 todeliver the second stimulation therapy. As another example, patient 14may use external programmer 24 to provide input that causes IMD 16 todeliver the second stimulation therapy. In this way, patient 14 maycontrol delivery of the second stimulation therapy.

IMD 16 delivers a first stimulation therapy and a second stimulationtherapy to patient 14 to generate different physiological responses. Forexample, the first stimulation therapy may generate an afferent responseby the patient, whereas the second stimulation therapy generates anefferent response. In some examples, IMD 16 delivers the firststimulation therapy to a sacral nerve of patient 14 to generate anafferent response that relaxes bladder 12, e.g., by minimizing bladdercontractions. In some examples, the delivery of the first stimulationtherapy by IMD 16 results in the closure or maintains the closure ofinternal urinary sphincter 13 at the neck of bladder 12.

In addition, in some examples, IMD 16 delivers the second stimulationtherapy to promote contraction of the internal urinary sphincter 13 andexternal urinary sphincter 11 or periurethral muscles (not shown). Insome cases, it is undesirable for the external urinary sphincter orperiurethral muscles to always remain closed, i.e., during the deliveryof the chronic, first stimulation therapy. However, sphincter closuremay help prevent the involuntary leakage of urine from bladder 12. Thus,the short-term closure of sphincter provided by the second stimulationtherapy may help prevent the occurrence of involuntary voiding eventsduring the occurrence of acute bladder contractions. In the exampleshown in FIG. 1, IMD 16 generates and delivers a first stimulationtherapy and a second stimulation therapy to patient 14 according todifferent sets of stimulation parameters.

In the example of FIG. 1, IMD 16 delivers both the first and secondstimulation therapies to patient 14 via electrodes 29 on lead 28. Thetarget therapy site for the first and second stimulation therapies maybe the same in some examples, such as the different fibers of the samenerve. In other examples, the target stimulation site for the first andsecond stimulation therapies may be different. For example, IMD 16 maydeliver the first stimulation therapy to a sacral nerve of patient 14 torelax bladder 12 and deliver the second stimulation therapy to ahypogastric nerve to contract the internal urinary sphincter andexternal urinary sphincter or periurethral muscles, a pudendal nerve, adorsal penile nerve in a male patient or a dorsal clitoral nerve in afemale patient to contract the external urinary sphincter, periurethralmuscles, the internal urinary sphincter, or any combination thereof. Inother examples, IMD 16 may deliver the first stimulation therapy to ahypogastric nerve of patient 14 to close or maintain internal urinarysphincter closure or urethral tone.

IMD 16 may be surgically implanted in patient 14 at any suitablelocation within patient 14, such as near the pelvis. The implantationsite may be a subcutaneous location in the side of the lower abdomen orthe side of the lower back or upper buttocks. IMD 16 has a biocompatiblehousing, which may be formed from titanium, stainless steel, a liquidcrystal polymer, or the like. The proximal ends of leads 18, 20, and 28are both electrically and mechanically coupled to IMD 16 either directlyor indirectly, e.g., via a respective lead extension. Electricalconductors disposed within the lead bodies of leads 18, 20, and 28electrically connect sense electrodes (not shown) and stimulationelectrodes, such as electrodes 29, to a therapy delivery module (e.g., astimulation generator) within IMD 16. In the example of FIG. 1, leads 18and 20 carry electrodes 19A, 19B (collective referred to as “electrodes19”) and electrodes 21A, 21B (collectively referred to as “electrodes21”), respectively. As described in further detail below, electrodes 19and 21 may be positioned for sensing an impedance of bladder 12, whichmay decrease as the volume of urine within bladder 12 increases.

One or more medical leads, e.g., leads 18, 20, and 28, may be connectedto IMD 16 and surgically or percutaneously tunneled to place one or moreelectrodes carried by a distal end of the respective lead at a desiredpelvic nerve or muscle site, i.e., one of the previously listed targettherapy sites such as a sacral or pudendal nerve. For example, lead 28may be positioned such that electrodes 29 deliver a first type ofstimulation therapy to a sacral or pudendal nerve to relax bladder 12and deliver the second type of stimulation therapy to hypogastric nerve,a pudendal nerve, a dorsal penile/clitoral nerve, the urinary sphincter,or any combination thereof to a promote closure of a urinary sphincterof patient 14. In FIG. 1, leads 18 and 20 are placed proximate to anexterior surface of the wall of bladder 12 at first and secondlocations, respectively. Electrodes 29 of the common lead 28 may deliverstimulation to the same or different nerves. In other examples oftherapy system 10, IMD 16 may be coupled to more than one lead thatincludes electrodes for delivery of electrical stimulation to differentstimulation sites within patient 14, e.g., to target different nerves.

In the example shown in FIG. 1, leads 18, 20, 28 are cylindrical.Electrodes 19, 20, 29 of leads 18, 20, 28, respectively, may be ringelectrodes, segmented electrodes or partial ring electrodes. Segmentedand partial ring electrodes each extend along an arc less than 360degrees (e.g., 90-120 degrees) around the outer perimeter of therespective lead 18, 20, 28. In examples, one or more of leads 18, 20, 28may be, at least in part, paddle-shaped (i.e., a “paddle” lead). In someexamples, segmented electrodes 29 of lead 28 may be useful for targetingdifferent fibers of the same or different nerves to generate differentphysiological effects for the first and second stimulation therapies. Asdescribed in further detail below, segmented electrodes may be usefulfor delivering relatively high frequency stimulation (e.g., about 66Hertz) and relatively low frequency stimulation (e.g., about 15 Hertz)to activate both fast twitch muscles and low twitch musclessubstantially simultaneously or at alternating time slots.

In some examples, one or more of electrodes 19, 20, 29 may be cuffelectrodes that are configured to extend at least partially around anerve (e.g., extend axially around an outer surface of a nerve).Delivering stimulation via one or more cuff electrodes and/or segmentedelectrodes may help achieve a more uniform electrical field oractivation field distribution relative to the nerve, which may helpminimize discomfort to patient 14 that results from the delivery of thefirst and/or second stimulation therapies. An electrical fieldrepresents the areas of a patient anatomical region that will be coveredby an electrical field during delivery of stimulation therapy to tissuewithin patient 14. The electrical field may define the volume of tissuethat is affected when the electrodes 19, 20, 29 are activated. Anactivation field represents the neurons that will be activated by theelectrical field in the neural tissue proximate to the activatedelectrodes.

In some cases, patient 14 may perceive the delivery of the secondstimulation therapy because of the increased intensity (e.g., increasedamplitude and/or frequency) compared to the first stimulation therapy.The increased intensity of the second stimulation therapy may result ina change in an electrical field and/or activation field that isgenerated via the stimulation therapy compared to the delivery of thefirst stimulation therapy. Delivering the first and/or secondstimulation therapies via cuff and/or segmented electrodes to achieve amore uniform electrical field or activation field distribution may helpdecrease changes in the intensity of therapy delivery perceived bypatient 14.

The illustrated numbers and configurations of leads 18, 20, and 28 andelectrodes carried by leads 18, 20, and 28 are merely exemplary. Otherconfigurations, i.e., number and position of leads and electrodes arepossible. For example, in other examples, IMD 16 may be coupled toadditional leads or lead segments having one or more electrodespositioned at different locations in the pelvic region of patient 14.The additional leads may be used for delivering first or secondstimulation therapies to respective stimulation sites within patient 14or for monitoring physiological parameters of patient 14. As an example,in an example in which the target therapy sites for the first and secondstimulation therapies are different, IMD 16 may be coupled to two ormore leads, e.g., for bilateral or multi-lateral stimulation.

As previously indicated, IMD 16 generates and delivers a firstelectrical stimulation therapy to a patient to generate a firstphysiological effect to manage urinary or fecal incontinence and, whentriggered, a second electrical stimulation therapy to provide anadditional boost of therapy that generates a second physiological effectto help further manage urinary or fecal incontinence. IMD 16 controlsthe delivery of the second electrical stimulation therapy based on inputreceived from patient 14 or a sensor that generates a signal indicativeof a parameter of patient 14 relating to urinary incontinence, e.g.,relating to a bladder condition, or fecal incontinence. As one example,IMD 16 may deliver the second stimulation therapy in response todetecting bladder contraction based on bladder impedance, bladderpressure, pudendal or sacral afferent nerve signals, a urinary sphincterEMG, or any combination thereof. As another example, IMD 16 may deliverthe second stimulation therapy in response to detecting a patientactivity level or patient posture state, with a sensor, which isindicative of an increased probability of an occurrence of aninvoluntary voiding event.

In some examples, IMD 16 may deliver the second stimulation therapy inresponse to receiving patient input. In this way, patient 14 may useexternal programmer 24 to trigger IMD 16 to deliver the secondstimulation therapy. Patient 14 may initiate the delivery of the secondstimulation therapy for many reasons. In some cases, patient 14 may beafflicted with urge incontinence, and upon perceiving an urge to void,patient 14 may provide input that causes IMD 16 to deliver the secondstimulation therapy. The second stimulation therapy provides anadditional “boost” of stimulation that helps prevent the leakage ofurine from bladder 12, e.g., by contracting internal urinary sphincter13 and the external urinary sphincter 11. In this way, therapy system 10provides patient 14 with direct control of the incontinence therapy.

IMD 16 delivers both the first and second stimulation therapies viaelectrodes 29 on lead 28. In the example shown in FIG. 1, IMD deliversthe second stimulation therapy to generate the second physiologicalresponse when contraction of bladder 12 exceeding a particular thresholdis detected. In the illustrated example of FIG. 1, IMD 16 determines animpedance through bladder 12, which varies as a function of thecontraction of bladder 12, via electrodes 19 and 21 on leads 18 and 20,respectively. In the example shown in FIG. 1, IMD 16 determines bladderimpedance using a four-wire (or Kelvin) measurement technique. In otherexamples, IMD 16 may measure bladder impedance using a two-wire sensingarrangement. In either case, IMD 16 may transmit an electricalmeasurement signal, such as a current, through bladder 12 via leads 18and 20, and determine bladder impedance based on the transmittedelectrical signal.

In the example four-wire arrangement shown in FIG. 1, electrodes 19A and21A and electrodes 19B and 21B, may be located substantially oppositeeach other relative to the center of bladder 12. For example electrodes19A and 21A may be placed on opposing sides of bladder 12, eitheranterior and posterior or left and right. In FIG. 1, electrodes 19 and21 are shown placed proximate to an exterior surface of the wall ofbladder 12. In some examples, electrodes 18 and 21 may be sutured orotherwise affixed to the bladder wall. In other examples, electrodes 19and 21 may be implanted within the bladder wall. To measure theimpedance of bladder 12, IMD 16 may source an electrical signal, such ascurrent, to electrode 19A via lead 18, while electrode 21A via lead 20sinks the electrical signal. IMD 16 may then determine the voltagebetween electrode 19B and electrode 21B via leads 18 and 20,respectively. IMD 16 determines the impedance of bladder 12 using aknown value of the electrical signal sourced the determined voltage.

In the example of FIG. 1, IMD 16 also includes a sensor 22 for detectingchanges in the contraction of bladder 12. Sensor 22 may be, for example,a pressure sensor for detecting changes in bladder pressure, electrodesfor sensing pudendal or sacral afferent nerve signals, or electrodes forsensing urinary sphincter EMG signals (or anal sphincter EMG signals inexamples in which therapy system 10 provides therapy to manage fecalincontinence), or any combination thereof. In examples in which sensor22 is a pressure sensor, the pressure sensor may be a remote sensor thatwireless transmits signals to IMD 16 or may be carried on one of leads18, 20, or 28 or an additional lead coupled to IMD 16. In examples inwhich sensor 22 is one or more electrodes for sensing afferent nervesignals, the sense electrodes may be carried on one of leads 18, 20, or28 or an additional lead coupled to IMD 16. In examples in which sensor22 is one or more sense electrodes for generating a urinary sphincterEMG, the sense electrodes may be carried on one of leads 18, 20, or 28or additional leads coupled to IMD 16. In any case, IMD 16 may delivercontrol the timing of the delivery of the second stimulation therapybased on input received from sensor 22.

In other examples, sensor 22 may comprise a patient motion sensor thatgenerates a signal indicative of patient activity level or posturestate. In some examples, IMD 16 controls the delivery of the secondstimulation therapy to patient 14 upon detecting a patient activitylevel exceeding a particular threshold based on the signal from themotion sensor. The patient activity level that is greater than or equalto a threshold (which may be stored in a memory of IMD 16) may indicatethat there is an increase in the probability that an incontinence eventwill occur, and, therefore, the additional boost of stimulation therapyprovided by the second stimulation therapy is desirable. In this way,the second stimulation therapy provided by IMD 16 and the secondphysiological effect provided by the second stimulation therapy (e.g.,the contraction of external urinary sphincter 11) may be useful forreacting to the circumstances that may affect patient incontinence andprovide an additional layer of therapy to help prevent the occurrence ofan involuntary voiding event.

In other examples, IMD 16 controls the delivery of the secondstimulation therapy to patient 14 upon detecting a posture stateassociated with a high probability of an occurrence of an incontinenceevent based on the signal from the motion sensor. For example, patient14 may be more prone to an incontinence event when patient 14 is in anupright posture state compared to a lying down posture state. IMD 16may, for example, store a plurality of motion sensor signals andassociate the signals with particular patient posture states using anysuitable technique. IMD 16 may flag some of the posture states as beingposture states for which additional therapy to help prevent theoccurrence of an incontinence event is desirable.

System 10 may also include an external programmer 24, as shown inFIG. 1. In some examples, programmer 24 may be a wearable communicationdevice, with boost function (e.g., activation of the second stimulationtherapy) integrated into a key fob or a wrist watch, handheld computingdevice, computer workstation, or networked computing device. Programmer24 may include a user interface that receives input from a user (e.g.,patient 14, a patient caretaker or a clinician). The user interface mayinclude, for example, a dedicated “boost button” to receive and confirmtherapy delivery according to the second stimulation therapy, a keypadand a display, which may for example, be a cathode ray tube (CRT)display, a liquid crystal display (LCD) or light emitting diode (LED)display. The keypad may take the form of an alphanumeric keypad or areduced set of keys associated with particular functions. Programmer 24can additionally or alternatively include a peripheral pointing device,such as a mouse, via which a user may interact with the user interface.In some examples, a display of programmer 24 may include a touch screendisplay, and a user may interact with programmer 24 via the display. Itshould be noted that the user may also interact with programmer 24and/or ICD 16 remotely via a networked computing device.

Patient 14 may interact with programmer 24 to control IMD 16 to deliverthe second stimulation therapy, to manually abort the delivery of thesecond stimulation therapy by IMD 16 while IMD 16 is delivery thetherapy or is about to deliver the therapy, or to inhibit the deliveryof the second stimulation therapy by IMD 16, e.g., during voluntaryvoiding events. Patient 14 may, for example, use a keypad or touchscreen of programmer 24 to cause IMD 16 to deliver the secondstimulation therapy, such as when patient 14 senses that a leakingepisode may be imminent. In this way, patient 14 may use programmer 24to control the delivery of the second stimulation therapy “on demand,”e.g., when an extra boost of the stimulation therapy is desirable.

In some examples, patient 14 may interact with IMD 16 (e.g., viaprogrammer 24 or directly via IMD 16) to control IMD 16 to deliver thesecond stimulation therapy, manually abort the delivery of the secondstimulation therapy, or inhibit the delivery of the second stimulationtherapy. In such examples, a motion sensor can be integrated into or ona housing of IMD 16, whereby the motion sensor generates a signal thatis indicative of patient 14 tapping IMD 16 through the skin. The number,rate, or pattern of taps may be associated with the differentprogramming capabilities, and IMD 16 may identify the tapping by patient14 to determine when patient input is received. In this way, patient 14may be able to directly control delivery of therapy in the event thatprogrammer 24 is not within reach of patient 14.

In some examples, programmer 24 may provide a notification to patient 14when the second stimulation therapy is being delivered or notify patient14 of the prospective delivery of the second stimulation therapy toallow patient 14 to manually abort the second stimulation therapy. Insuch examples, programmer 24 may display a visible message, emit anaudible alert signal or provide a somatosensory alert (e.g., bycontrolling a housing of programmer 24 to vibrate). After generating thenotification, programmer 24 may wait for input from patient 14 prior todelivering the second stimulation therapy. Patient 14 may enter inputthat either confirms delivery of the second stimulation therapy ispermitted or desirable, or manually aborts the prospective delivery ofthe second stimulation therapy. In the event that no input is receivedwithin a particular range of time, programmer 24 may wirelessly transmita signal that indicates the absence of patient input to IMD 16. IMD 16may then elect to deliver or not to deliver the second stimulationtherapy based on the programming of IMD 16. Patient 14 may also interactwith programmer 24 to inhibit the delivery of the second stimulationtherapy during voluntary voiding events. That is, patient 14 may useprogrammer 24 to enter input that indicates the patient will be voidingvoluntarily. When IMD 16 receives the input from programmer 24, IMD 16may suspend delivery the second stimulation therapy for a predeterminedperiod of time, e.g., two minutes, to allow the patient to voluntarilyvoid.

A user, such as a physician, technician, surgeon, electrophysiologist,or other clinician, may also interact with programmer 24 or anotherseparate programmer (not shown), such as a clinician programmer tocommunicate with IMD 16. Such a user may interact with a programmer toretrieve physiological or diagnostic information from IMD 16. The usermay also interact with a programmer to program IMD 16, e.g., selectvalues for the stimulation parameter values with which IMD 16 generatesand delivers stimulation and/or the other operational parameters of IMD16. For example, the user may use a programmer to retrieve informationfrom IMD 16 regarding the contraction of bladder 12 and voiding events.As another example, the user may use a programmer to retrieveinformation from IMD 16 regarding the performance or integrity of IMD 16or other components of system 10, such as leads 18, 20, and 28, or apower source of IMD 16. In some examples, this information may bepresented to the user as an alert if a system condition that may affectthe efficacy of therapy is detected.

IMD 16 and programmer 24 may communicate via wireless communicationusing any techniques known in the art. Examples of communicationtechniques may include, for example, low frequency or radiofrequency(RF) telemetry, but other techniques are also contemplated. In someexamples, programmer 24 may include a programming head that may beplaced proximate to the patient's body near the IMD 16 implant site inorder to improve the quality or security of communication between IMD 16and programmer 24.

IMD 16 does not deliver the second stimulation therapy to patient 14 ona predetermined, scheduled basis, but as needed. For example, IMD 16 candeliver the second stimulation therapy to patient 14 when a particularpatient parameter (e.g., a physiological parameter, activity level orposture state) indicative of a high probability of an occurrence of aninvoluntary voiding event is detected or when patient input is received.In some examples, either IMD 16 or programmer 24 may track when IMD 16delivers the second stimulation therapy to patient 14. Frequent deliveryof the second stimulation therapy may be undesirable because, forexample, muscle fatigue may result. Frequent delivery of the secondstimulation therapy may indicate that, as another example, bladder 12 isfull.

In some examples, programmer 24 may provide a notification to patient 14when the second stimulation therapy is triggered too frequently. Thenotification may be triggered based on any suitable criteria, which maybe determined by a clinician or automatically programmed into IMD 16 orprogrammer 24. For example, in the event that the second stimulationtherapy is triggered five times within five minutes, programmer 24 mayprovide a notification to patient 14 indicating the same. This may allowpatient 14 to proceed to a bathroom before a leaking episode occurs. Thenotification provided by programmer 24 may also direct patient 14 tovoluntarily void.

FIG. 2 is conceptual diagram illustrating another example therapy system30 that delivers a first stimulation therapy to provide a firstphysiological response to manage a urinary incontinence condition ofpatient 14, and a second stimulation therapy to provide a second,different physiological response to manage the urinary incontinencecondition of patient 14. Therapy system 30 includes a distributed arrayof electrical stimulators, referred to herein as microstimulators32A-32D (collectively referred to as “microstimulators 32”), in additionto IMD 16, leads 18, 20, and 28, sensor 22, and programmer 24.Microstimulators 32 are configured to generate and deliver electricalstimulation therapy to patient 14 vie one or more electrodes.Microstimulators 32 have a smaller size than IMD 16, and are typicallyleadless.

IMD 16 may deliver one or both of the first or second electricalstimulation therapies to patient 14 via microstimulators 32. Forexample, IMD 16 may communicate wirelessly with microstimulators 32 viawireless telemetry to control delivery of the first and/or secondstimulation therapies via microstimulators 32. In the example of FIG. 2,microstimulators 32 are implanted at different target stimulation sites.For example, microstimulators 32A and 32B may be positioned to stimulatea different set of nerves than microstimulators 32C and 324D. As anexample, microstimulators 32A and 32B may target sacral nerves, whilemicrostimulators 32C and 32D target the pudendal nerve. In otherexamples, microstimulators 32 may be implanted at various locationswithin the pelvic floor region, e.g., at different positions inproximity to the sacrum to target different nerves within the pelvicregion. The illustrated number and configuration of microstimulators 32is merely exemplary. Other configurations, i.e., number and position ofmicrostimulators, are possible.

Systems 10 and 30 shown in FIGS. 1 and 2, respectively, are merelyexamples of therapy systems that may provide a first stimulation therapyto provide a first physiological response to manage urinary or fecalincontinence, and a second stimulation therapy to provide a second,different physiological response to complement and “boost” the firststimulation therapy. Systems with other configurations of leads,electrodes, and sensors are possible. Additionally, in other examples, asystem may include more than one IMD. For example, a system may includean IMD coupled to one or more leads for delivering the first stimulationtherapy and another IMD coupled to one or more leads for delivering thesecond stimulation therapy.

FIG. 3 is a block diagram illustrating example components of IMD 16. Inthe example of FIG. 3, IMD 16 includes sensor 22, processor 50, therapydelivery module 52, impedance module 54, memory 56, telemetry module 58,and power source 60. Memory 56 stores first stimulation therapy programs66 and second stimulation therapy programs 68 that specify stimulationparameters for the first and second stimulation therapies, respectively.Memory 56 also stores bladder data 69, which processor 50 may use forcontrolling the timing of the delivery of the second stimulationtherapy. For example, bladder data 69 may include threshold values forone or more of bladder impedance, bladder pressure, sacral or pudendalafferent nerve signals, and external urinary sphincter or anal sphincterEMG templates.

Generally, therapy delivery module 52 generates and delivers therapyunder the control of processor 50. In particular, processor 50 controlstherapy delivery module 52 by accessing memory 56 to selectivelyaccessing and loading first and second stimulation therapy programs 66,68 to therapy delivery module 52. For example, in operation, processor50 may access memory 56 to load one of first stimulation therapyprograms 66 to therapy delivery module 52 and, when triggered, accessmemory 56 to load one of the second stimulation therapy programs 68 totherapy delivery module 52. Consistent with the techniques described inthis disclosure, processor 50 may load one of second stimulation therapyprograms 68 to therapy delivery module 52 based on input received fromimpedance module 54, sensor 22, or an indication of patient inputreceived from another device and transmitted to IMD 16 via telemetrymodule 58.

By way of example, processor 50 may access memory 56 to load one offirst stimulation therapy programs 66 to therapy module 52 fordelivering the first stimulation therapy to patient 14. A clinician orpatient 14 may select a particular one of first stimulation therapyprograms 66 from a list using a programming device, such as programmer24 or a clinician programmer. Processor 50 may receive the selection viatelemetry module 58. Therapy delivery module 52 delivers the firststimulation therapy to patient 14 according to the selected program foran extended period of time, such as hours, days, weeks, or until patient14 or a clinician manually stops or changes the program. The firststimulation therapy program 66 may define a schedule or an “on cycle”and “off cycle” duration for the first stimulation therapy, such that astimulation signal is not continuously delivered to patient 14, butperiodically delivered in accordance with predetermined parameters forthe first stimulation therapy.

Upon detecting a condition in which the second stimulation therapy isdesirable to help prevent the occurrence of an incontinence event, suchas in response to detecting bladder contractions or receiving patientinput, processor 50 accesses memory 56 to load one of second stimulationtherapy programs 68 to therapy delivery module 52. Therapy deliverymodule 52 delivers the second stimulation therapy according to theselected program. In some examples, therapy module 52 delivers thesecond stimulation therapy for a predetermined therapy period, theduration of which may be stored in memory 56. The therapy period may be,for example, approximately 10 seconds to approximately 50 seconds,although other therapy periods are contemplated. That is, therapydelivery module 52 may deliver therapy according to second stimulationtherapy programs 68 via bursts of stimulation for a duration ofapproximately 10 seconds to approximately 60 seconds and subsequentlyreverts to delivering therapy according to one of first stimulationtherapy programs 66.

In some examples, therapy module 52 delivers the second stimulationtherapy for a period of time controlled by the patient. In suchexamples, the patient may interact with programmer 24 to control thedelivery time. As an example, IMD 16 may deliver the second stimulationtherapy as long as the patient presses a “boost” button on a keypad ortouch screen of programmer 24. In operation, processor 50 receives thepatient input via telemetry module 58 and controls therapy deliverymodule 52 to deliver therapy according to the received input.

In other examples, such as examples in which IMD 16 delivers the secondstimulation therapy based on a sensed patient condition, therapy module52 delivers the second stimulation therapy until the condition is nolonger detected. For example, IMD 16 may deliver the second stimulationtherapy in response to detecting a bladder impedance greater than orequal to a predetermined threshold and continue delivering the secondstimulation therapy until the bladder impedance is less than thepredetermined threshold. If the second stimulation therapy is deliveredfor more than one consecutive therapy, IMD 16 may separate theconsecutive therapy periods by at least a predetermined minimuminter-therapy interval. In some examples, the minimum inter-therapyinterval is about 10 seconds, although other intervals are contemplated.

In some examples, IMD 16 delivers the second stimulation therapy atsubstantially the same time as the first stimulation therapy, such thatthe first and second physiological effects from the first and secondstimulation therapy, respectively, overlap. In other examples, the firstand second stimulation therapies are not delivered at the same time,such that IMD 16 only delivers one type of therapy at a time. Thealternating therapies may be implemented if, for example, IMD 16delivers the first and second stimulation therapies with a common set ofelectrodes. In the latter technique, when the second stimulation therapyhas been delivered, IMD 16 may revert back to delivering the firststimulation therapy according to a first stimulation therapy program 66selected from memory 56.

Therapy module 52 delivers therapy, i.e., electrical stimulation,according to stimulation parameters, such as voltage or currentamplitude, pulse rate (frequency), and pulse width specified by therapyprograms, such as first stimulation therapy programs 66 and secondstimulation therapy programs 68. In some examples, therapy deliverymodule 52 delivers therapy in the form of electrical pulses. In otherexamples, therapy delivery module 52 delivers electrical stimulation inthe form of continuous waveforms.

In some examples, the stimulation parameters for the first stimulationprograms 66 may be selected to relax bladder 12 (FIG. 1) or close ormaintain internal urinary sphincter closure or urethral tone. An examplerange of stimulation parameters for the first stimulation therapy thatare likely to be effective in treating incontinence, e.g., when appliedto the sacral or pudendal nerves, are as follows:

1. Frequency: between approximately 0.5 Hz and approximately 500 Hz,such as between approximately 10 Hz and approximately 250 Hz, or betweenapproximately 10 Hz and approximately 25 Hz.

2. Amplitude: between approximately 0.1 volts and approximately 50volts, such as between approximately 0.5 volts and approximately 20volts, or between approximately 1 volt and approximately 10 volts.

3. Pulse Width: between approximately 10 microseconds (μs) andapproximately 5000 μs, such as between approximately 100 μs andapproximately 1000 μs, or between approximately 180 μs and approximately450 μs.

The stimulation parameters for second stimulation therapy programs 68are generally different than those for first stimulation therapyprograms 66. Stimulation parameters for second stimulation therapyprograms 68 may be selected to maximize closure of one or more ofinternal urinary sphincter, external urinary sphincter, and periurethralmuscles. Stimulation parameters for second stimulation therapy programs68 may also be selected to minimize muscle fatigue. Muscle fatigue mayoccur when the force-generating ability of a muscle decreases as aresult of the electrical stimulation.

An example range of stimulation pulse parameters for the secondstimulation therapy are as follows:

1. Frequency: between approximately 15 Hz to approximately 30 Hz toactivate slow-twitch muscles to minimize muscle fatigue while providingsome sphincter closure, and between approximately 30 Hz andapproximately 66 Hz to activate fast-twitch muscles, which may maximizesphincter closure.

2. Amplitude: approximately 2-8 times rheobase (e.g., approximately 2-4times rheobase) for the target nerve or muscle (e.g., the sphinctermuscle), such as about 0.5 volts to about 50 volts, or about 0.5 voltsto about 10 volts, or about 4 volts to about 8 volts. Rheobase is theminimal electric current of infinite duration that results in an actionpotential or muscle twitch.

3. Pulse Width: between about 10 microseconds (μs) and about 5,000 μs,such as between about 100 μs and approximately 1,000 μs.

As previously indicated, IMD 16 may deliver the second stimulationtherapy for duration of time referred to as a therapy period. In someexamples, the therapy period has a duration of about 10 seconds to about50 seconds, although other therapy period durations are contemplated. Insome examples, the therapy period duration is controlled by patient 14through programmer 24, and may have a maximum period limit of about 3minutes, although other maximum therapy periods for the secondstimulation therapy is contemplated.

At least one of second stimulation therapy programs 68 may include morethan one set of stimulation parameters. In such examples, one set ofstimulation parameters may be designed to activate fast-twitch musclefibers in order to maximize closure of the urinary sphincter and/orperiurethral muscles, and another set of stimulation parameters may bedesigned to activate slow-twitch muscle fibers in order to maintainclosure of the urinary sphincter and/or periurethral muscles whileminimizing muscle fatigue. The fast-twitch and slow-twitch muscle fibersmay be selectively activated by activating specific nerve fibers withthe same electrodes of a common lead, or different electrodes of acommon lead (e.g., segmented electrodes specifically selected to targetparticular nerve fibers) or electrodes of separate leads ormicrostimulators.

As an example, in accordance with one of the second stimulation therapyprograms 68, IMD 16 may generate and deliver stimulation pulses having arelatively high frequency (e.g., about 66 Hz) for the first five secondsof the therapy interval to activate fast-twitch muscle fibers, andsubsequently generate and deliver stimulation pulses at a lower relativefrequency (e.g., 30 Hz) for the following 10 seconds to activateslow-twitch muscle fibers. An example stimulation signal that IMD 16 maygenerate and deliver as part of the second stimulation therapy isdescribed with respect to in FIG. 11.

In some examples, the portion of the second stimulation therapy thatactivates the fast twitch muscles is delivered for a shorter duration oftime than the portion of the second stimulation therapy that activatesthe slow twitch muscles. This may help minimize muscle fatigue byproviding the fast twitch muscles with a longer recovery time. It hasbeen found that some fast twitch muscles require a longer time torecover, e.g., to regain contraction force, following the delivery ofstimulation, than slow twitch muscles. Muscles may be recovered when thecontraction force under stimulation is close or substantially equal tothe contraction force under the same stimulation intensity while thereis no fatigue e.g., when the muscles are stimulated a first time after arelatively long time of rest in which no stimulation was delivered. Ifthe muscle is stimulated again with the same therapy parameter values,and the contraction force is the same, then the muscle may be consideredto have recovered from the previous delivery of stimulation.

In some examples, processor 50 may control the timing of the secondstimulation therapy relative to the first stimulation therapy in amanner that minimizes muscle fatigue. For example, processor 50 mayutilize an inter-therapy interval to prevent the second stimulationtherapy from being delivered so frequently that the pelvic musclesfatigue and render second stimulation therapy less effective or evenineffective. The inter-therapy interval is a predetermined amount oftime, e.g., 10 seconds, following a delivery of a therapy period of thesecond stimulation therapy during which IMD 16 cannot deliver asubsequent therapy period of the second stimulation therapy. In thisway, in some examples, the second stimulation therapy cannot betriggered within a minimal inter-therapy interval following previouslydelivered second stimulation therapy to prevent muscle fatigue. Thus, ifthe second stimulation therapy is triggered within the inter-therapyinterval (e.g., based on a sensed patient parameter or patient input)processor 50 of IMD 16 may control therapy delivery module 52 togenerate and deliver the second stimulation therapy only after theinter-therapy interval has lapsed. Alternatively, processor 50 mayignore sensor input (e.g., input from impedance module 54) or patientinput received via telemetry module 58 for the duration of theinter-therapy interval. An example of the application of theinter-therapy interval is provided in FIG. 12.

In some examples, processor 50 may adjust a second stimulation therapyprogram 68 for one or more consecutive therapy periods to configure thesecond stimulation therapy to minimize muscle fatigue. In this way, IMD16 may provide second stimulation therapy that is delivered in anadaptive fashion. In some examples, processor 50 may implement aninter-therapy interval, but rather than abstaining from delivery of thesecond stimulation therapy when the second stimulation therapy istriggered within an inter-therapy interval, processor 50 controlstherapy delivery module 52 to generate and deliver stimulation accordingto an adjusted second stimulation therapy.

As one example, if second stimulation therapy is triggered within theinter-therapy interval following the delivery of a previous secondstimulation therapy, the adaptive stimulation program may decrease theduration of fast-twitch muscle stimulation defined by thepreviously-implemented second stimulation therapy program by a firsttime increment (e.g., five seconds) and increase the duration ofslow-twitch muscle stimulation by the same or different time increment.As another example, for each second stimulation therapy triggered withinan inter-therapy interval, the adaptive stimulation program may replacethe first five second of fast-twitch muscle stimulation by five secondof slow-twitch muscle stimulation compared to the previously deliveredthe second stimulation therapy signal. Example adaptive stimulationsignals that may be delivered as part of the second stimulation therapyare described below with respect to FIGS. 13A-13C and 14A-14C.

In other examples, second stimulation therapy programs 68 may define thesimultaneous delivery of stimulation at multiple frequencies. As anexample, a stored second stimulation therapy program 68 may definesegmented electrodes to simultaneously deliver higher frequency (e.g.,66 Hz) stimulation to fascicles responsible for fast muscles, such asthe Iliococcygeus muscle and the pubococcygeus muscle, and lowerfrequency stimulation (e.g., 30 Hz) to fascicles responsible for slowmuscles, such as the soleus muscle.

In the example of FIG. 3, therapy delivery module 52 drives a singlelead 28. Specifically, therapy delivery module 52 delivers electricalstimulation to tissue of patient 14 via selected electrodes 29A-29Dcarried by lead 28. A proximal end of lead 28 extends from the housingof IMD 16 and a distal end of lead 28 extends to target therapy siteswithin the pelvic floor, such as tissue sites proximate a sacral nerve,a pudendal nerve, a hypogastric nerve, a urinary sphincter, or anycombination thereof. In other examples, therapy delivery module 52 maydeliver electrical stimulation with electrodes on more than one lead andeach of the leads may carry one or more electrodes. The leads may beconfigured as an axial leads with ring electrodes and/or paddle leadswith electrode pads arranged in a two-dimensional array. The electrodesmay operate in a bipolar or multi-polar configuration with otherelectrodes, or may operate in a unipolar configuration referenced to anelectrode carried by the device housing or “can” of IMD 16. In yet otherexamples, such as system 30 shown in FIG. 2 that includesmicrostimulators 32, processor 50 may act as a “master” module thatcontrols microstimulators to deliver stimulation at target therapysites. In other examples, however, one of microstimulators 32 may act asa master module or microstimulators 32 may be self-controlled.

In some examples, processor 50 controls therapy module 52 to deliver thesecond stimulation therapy to patient 14 based on signals received fromimpedance module 54, sensor 22, or patient input received via telemetrymodule 58. In the example shown in FIG. 3, processor 50 monitors bladderimpedance to detect bladder contraction based on signals received fromimpedance module 54. For example, processor 50 may determine animpedance value based on signals received from impedance module 54 andcompare the determined impedance value to a threshold impedance valuestored in memory 56 as bladder data 69. When the determined impedancevalue is less than the threshold value stored in bladder data 69,processor 50 detects bladder contraction and loads one of secondstimulation therapy programs 68 in therapy module 52, and therapy module52 generates and delivers the second stimulation therapy to patient 14to generate a physiological response that helps prevent an incontinenceevent. As previously indicated, the physiological response generated bythe delivery of the second stimulation therapy differs from thephysiological response generated by the delivery of the firststimulation therapy to provide an additional layer of incontinenceprevention.

In the example of FIG. 3, impedance module 54 includes voltagemeasurement circuitry 62 and current source 64, and may include anoscillator (not shown) or the like for producing an alternating signal,as is known. In some examples, as described above with respect to FIG.1, impedance module 54 may use a four-wire, or Kelvin, arrangement. Asan example, processor 50 may periodically control current source 64 to,for example, source an electrical current signal through electrode 19Aand sink the electrical current signal through electrode 21A. In someexamples, for collection of impedance measurements, current source 64may deliver electrical current signals that do not deliver stimulationtherapy to bladder 12, e.g., sub-threshold signals, due to, for example,the amplitudes or widths of such signals and/or the timing of deliveryof such signals. Impedance module 54 may also include a switching module(not shown) for selectively coupling electrodes 19A, 19B, 21A, and 21Bto current source 64 and voltage measurement circuitry 62. Voltagemeasurement circuitry 62 may measure the voltage between electrodes 19Band 21B. Voltage measurement circuitry 62 may include sample and holdcircuitry or other suitable circuitry for measuring voltage amplitudes.Processor 50 determines an impedance value from the measure voltagevalues received from voltage measurement circuitry 52.

As previously described, sensor 22 may be a pressure sensor fordetecting changes in bladder pressure, electrodes for sensing pudendalor sacral afferent nerve signals, or electrodes for sensing externalurinary sphincter EMG signals (or anal sphincter signals in examples inwhich IMD 16 provides fecal incontinence therapy), or any combinationthereof. Alternatively, sensor 22 may be a motion sensor, such as atwo-axis accelerometer, three-axis accelerometer, one or moregyroscopes, pressure transducers, piezoelectric crystals, or othersensors that generate a signal that changes as patient activity level orposture state changes. Processor 50 may detect a patient conditionindicative of a high probability of an incontinence event (e.g., bladdercontraction or abnormal detrusor muscle activity) or other triggerevents based on signals received from sensor 22 in addition to insteadof impedance module 54. Sensor 22 may also be a motion sensor that isresponsive to tapping (e.g., by patient 14) on skin superior to IMD 16and, as previously described, processor 50 may control therapy module 52to deliver second stimulation therapy, manually abort delivery of secondstimulation therapy, or inhibit the delivery of second stimulationtherapy, in response to detection of the patient tapping.

One type of bladder contraction detection algorithm indicates anoccurrence of a bladder contraction for which delivery of the secondstimulation therapy is desirable upon sensing of a signal that exhibitsa certain characteristic, which may be a time domain characteristic(e.g., an amplitude) or a frequency domain characteristic (e.g., anenergy level in one or more frequency bands). For example, the bladdercontraction detection algorithm may indicate the occurrence of a bladdercontraction for which delivery of the second stimulation therapy isdesirable when the amplitude of the signal from sensor 22 meets acertain condition relative to a threshold (e.g., is greater than, equalto or less than the threshold). Another bladder contraction detectionalgorithm indicates the occurrence of a bladder contraction for whichdelivery of the second stimulation therapy is desirable if a sensedsignal substantially correlates to a signal template, e.g., in terms offrequency, amplitude and/or spectral energy characteristics. IMD 16 mayuse known techniques to correlate a sensed signal with a template inorder to detect the bladder contraction or detect the bladdercontraction based on the frequency domain characteristics of a sensedsignal. Other bladder contraction techniques may be used.

In examples in which sensor 22 includes a pressure sensor, processor 50may determine a pressure value based on signals received from thepressure sensor and compare the determined pressure value to a thresholdvalue stored in bladder data 69 to determine whether the contractions ofbladder 12 are indicative of an imminent incontinence event. In examplesin which sensor 22 includes an EMG sensor, processor 50 may generate anEMG from the received signals generated by sensor 22 (e.g., which maysense the muscle activity with one or more sensor positioned near thetarget muscle) and compare the EMG to templates stored as bladder datato determine whether the contractions of bladder 12 are indicative of animminent incontinence event. Alternatively, processor 50 may comparepreviously collected EMGs to a current EMG to detect changes over time.The techniques for detecting bladder contractions may also be applied todetecting abnormal detrusor muscle activities.

As described above, in examples in which processor 50 monitors a patientcondition indicative of bladder contraction, processor 50 may controltherapy delivery module 52 to generate and deliver the secondstimulation therapy to generate the second physiological response onlyif the bladder contraction is greater than a threshold level. Thethreshold level may indicate a bladder contraction intensity (e.g.,strength or frequency) that is indicative of an imminent involuntaryvoiding event or a relatively high probably an involuntary voiding eventwill occur. In some cases, the bladder contraction may be indicative ofa voluntary voiding event. Thus, in some examples, processor 50 cancontrol therapy delivery module 52 to generate and deliver the secondstimulation therapy if the bladder contraction is greater than firstthreshold level, but less than a second threshold level.

In examples in which sensor 22 includes a motion sensor, processor 50may determine a patient activity level or posture state based on asignal generated by sensor 22. For example, processor 50 may determine apatient activity level by sampling the signal from sensor 22 anddetermining a number of activity counts during a sample period, where aplurality of activity levels are associated with respective activitycounts. In one example, processor 50 compares the signal generated bysensor 22 to one or more amplitude thresholds stored within memory 56,and identifies each threshold crossing as an activity count.

Processor 50 may determine a patient posture state based on a signalfrom sensor 22 using any suitable technique. In one example, a posturestate may be defined as a three-dimensional space (e.g., a posture coneor toroid), and whenever a posture state parameter value, e.g., a vectorfrom a three-axis accelerometer of sensor 22 resides within a predefinedspace, processor 50 indicates that patient 14 is in the posture stateassociated with the predefined space.

Memory 56 may associate patient posture states or activity levels withthe second stimulation therapy, such that when processor 50 detects aposture state or activity level associated with the second stimulationtherapy, processor 50 controls therapy delivery module 52 to generateand deliver the second stimulation therapy to patient 14. Certainposture states or activity levels may be associated with a higherincidence of incontinence events. For example, patient 14 may have lesscontrol of the pelvic floor muscles when occupying an upright posturestate or when patient 14 is in a highly active state (e.g., as indicatedby a stored activity count or a threshold activity signal value). Thus,detection of these activity levels or posture states may be triggers forthe delivery of the second stimulation therapy.

The threshold values (also referred to as threshold levels) or templates(e.g., indicating a signal indicative of an imminent voiding event)stored in memory 56 as bladder data 69 may be determined using anysuitable technique. In some examples, the threshold values may bedetermined during implantation of IMD 16 or during a trial period in aclinician's office following the implant procedure. For example, aclinician may record impedance values during involuntary voiding eventsand use the recorded impedance values or values calculated based on therecorded values as threshold values. These threshold values may beadapted over time based on user input, e.g., via external programmer 24.As an example, patient 14 may indicate, via programmer 24, when aninvoluntary voiding event takes place. When the patient input isreceived, processor 50 may determine an impedance value during the eventor immediately prior to the event based in signals received fromimpedance module 54. A new threshold value may be determined using thisimpedance value. For example, the threshold value stored as bladder data69 may be a running average of impedance values measured duringinvoluntary voiding events.

In some examples, IMD 16 includes impedance sensing module 54 and notsensor 22, while in other examples, IMD 16 includes sensor 22, but notimpedance sensing module 54. Moreover, in some examples, sensor 22and/or impedance sensing module 54 may be physically separate from IMD16. Physically separate sensors may be useful in examples in whicheither sensor 22 and/or impedance sensing module 54 sense one or morephysiological parameters at a location that is not accessible by IMD 16or difficult to access by IMD 16.

Processor 50 may control therapy delivery module 52 to deliver thesecond stimulation therapy based on patient input received via telemetrymodule 58. Telemetry module 58 includes any suitable hardware, firmware,software or any combination thereof for communicating with anotherdevice, such as programmer 24 (FIG. 1). Under the control of processor50, telemetry module 58 may receive downlink telemetry, e.g., patientinput, from and send uplink telemetry, e.g., an alert, to programmer 24with the aid of an antenna, which may be internal and/or external.Processor 50 may provide the data to be uplinked to programmer 24 andthe control signals for the telemetry circuit within telemetry module58, and receive data from telemetry module 58.

Generally, processor 50 controls telemetry module 58 to exchangeinformation with medical device programmer 24. Processor 50 may transmitoperational information and receive stimulation programs or stimulationparameter adjustments via telemetry module 58. Also, in some examples,IMD 16 may communicate with other implanted devices, such asstimulators, control devices, or sensors, via telemetry module 58.

As previously described, telemetry module 58 may receive an indicationthat patient 14 provided input indicative of an imminent voiding eventor a desire for delivery of the “boost” of stimulation, e.g., the secondstimulation therapy, from programmer 24. Upon receiving the patientinput via telemetry module 58, processor 50 may control therapy deliverymodule 52 to generate and deliver the second stimulation therapy for apredetermined amount of time or until a particular patient condition isdetected, to manually abort the second stimulation therapy, or inhibitthe second stimulation therapy during voluntary voiding. Processor 50monitors patient input received via telemetry module 58 and takesappropriate action. For example, telemetry module 58 may receive inputfrom programmer 24 that indicates a specified one of second stimulationtherapy programs 68 should be selected for delivery of the secondstimulation therapy program. Upon receiving the input, processor 50loads the specified one of second stimulation therapy programs 68 totherapy module 52.

In an example in which telemetry module 58 receives patient input thatindicates the second stimulation therapy should be aborted, processor 50may transmit a signal to programmer 24 via telemetry module 58 to notifypatient 14 of the prospective delivery of the second stimulationtherapy. The notification may be provided, for example, within less thana minute (e.g., a few seconds) prior to the delivery of the secondstimulation therapy. This notification provides patient 14 with theopportunity to intervene if the second stimulation therapy is not deemednecessary by patient 14 or if patient 14 is voluntarily voiding and thesecond stimulation therapy may hinder the voluntary voiding attempt.Processor 50 may control therapy module 52 to revert back to deliveringthe first stimulation therapy if the patient manually aborts thedelivery of the second stimulation therapy.

Upon receiving the notification of the prospective delivery of thesecond stimulation therapy, patient 14 may also provide active inputthat indicates IMD 16 can deliver the second stimulation therapy orpatient 14 may merely not intervene to indicate IMD 16 should deliverthe second stimulation therapy. Upon receiving the input confirming thesecond stimulation therapy or lack of input aborting the secondstimulation therapy, processor 50 may load one of first stimulationtherapy programs 66 to therapy module 52.

In an example in which telemetry module 58 receives patient inputindicating a voluntary voiding event, processor 50 may suspend deliveryof the second stimulation therapy for a pre-determined period of time,e.g., 2 minutes. In response to receiving the input, processor 50 mayignore signals indicative of the patient parameter, such as impedancesignals received from impedance module 54. Processor 50 may ignore thesesignals for a predetermined period of time, such as approximately twominutes. After two minutes has elapse, processor 50 may continuemonitoring patient 14 to detect trigger events.

The processors described in this disclosure, such as processor 50 andprocessing circuitry in impedance module 54 and other modules, may beone or more digital signal processors (DSPs), general purposemicroprocessors, application specific integrated circuits (ASICs), fieldprogrammable logic arrays (FPGAs), or other equivalent integrated ordiscrete logic circuitry, or combinations thereof. The functionsattributed to processors described herein may be provided by a hardwaredevice and embodied as software, firmware, hardware, or any combinationthereof. In some examples, the processing circuitry of impedance module54 that determines an impedance based on a measured voltage and/orcurrent of a signal may be the same microprocessor, ASIC, DSP, or otherdigital logic circuitry that forms at least part of processor 50.

Memory 56 may also store instructions for execution by processor 50, inaddition to first and second stimulation therapy programs 66, 68, andbladder data 69. Information related to measured impedance anddetermined posture may be recorded for long-term storage and retrievalby a user, or used by processor 50 for adjustment of stimulationparameters, such as amplitude, pulse width, and pulse rate. Memory 56may include separate memories for storing instructions, electricalsignal information, stimulation programs, and bladder data.

Memory 56 may include any volatile, non-volatile, magnetic, optical, orelectrical media, such as a random access memory (RAM), read-only memory(ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM(EEPROM), flash memory, and the like. Memory 56 may store programinstructions that, when executed by processor 50, cause IMD 16 toperform the functions ascribed to IMD 16 herein.

Power source 60 delivers operating power to the components of IMD 16.Power source 60 may include a battery and a power generation circuit toproduce the operating power. In some examples, the battery may berechargeable to allow extended operation. Recharging may be accomplishedthrough proximal inductive interaction between an external charger andan inductive charging coil within IMD 16. In other examples, an externalinductive power supply may transcutaneously power IMD 16 wheneverstimulation therapy is to occur.

FIG. 4 is a block diagram illustrating example components of externalprogrammer 24. While programmer 24 may generally be described as ahand-held computing device, the programmer may be a notebook computer, acell phone, or a workstation, for example. As illustrated in FIG. 4,external programmer 24 may include a processor 70, memory 72, userinterface 74, telemetry module 76, and power source 78. Memory 72 maystore program instructions that, when executed by processor 70, causeprocessor 70 and external programmer 24 to provide the functionalityascribed to external programmer 24 throughout this disclosure.

In some examples, memory 72 may further include program information,i.e., therapy programs defining the first type of stimulation therapyand therapy programs defining the second type of stimulation therapysimilar to those stored in memory 56 of IMD 16. The stimulation programsstored in memory 72 may be downloaded into memory 56 of IMD 16. Memory72 may include any volatile, non-volatile, fixed, removable, magnetic,optical, or electrical media, such as RAM, ROM, CD-ROM, hard disk,removable magnetic disk, memory cards or sticks, NVRAM, EEPROM, flashmemory, and the like. Processor 70 can take the form one or moremicroprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, orthe like, and the functions attributed to processor 70 herein may beembodied as hardware, firmware, software or any combination thereof.

User interface 74 may include a button or keypad, lights, a speaker forvoice commands, a display, such as a liquid crystal (LCD),light-emitting diode (LED), or cathode ray tube (CRT). In some examplesthe display may be a touch screen. As discussed in this disclosure,processor 70 may present and receive information relating to stimulationtherapy via user interface 74. For example, processor 70 may receivepatient input via user interface 74. The input may be, for example, inthe form of pressing a button on a keypad or selecting an icon from atouch screen.

Processor 70 may also present information to the patient in the form ofalerts related to delivery of the second stimulation therapy to patient14 or a caregiver, as will be described in more detail below, via userinterface 74. Although not shown, external programmer 24 mayadditionally or alternatively include a data or network interface toanother computing device, to facilitate communication with the otherdevice, and presentation of information relating to first and secondstimulation therapies via the other device.

Telemetry module 78 supports wireless communication between IMD 16 andexternal programmer 24 under the control of processor 70. Telemetrymodule 78 may also be configured to communicate with another computingdevice via wireless communication techniques, or direct communicationthrough a wired connection. Telemetry module 78 may be substantiallysimilar to telemetry module 58 described above, providing wirelesscommunication via an RF or proximal inductive medium. In some examples,telemetry module 78 may include an antenna, which may take on a varietyof forms, such as an internal or external antenna. An external antennathat is coupled to programmer 24 may correspond to a programming headthat may be placed over IMD 16.

Examples of local wireless communication techniques that may be employedto facilitate communication between programmer 24 and another computingdevice include RF communication according to the 802.11 or Bluetoothspecification sets, infrared communication, e.g., according to the IrDAstandard, or other standard or proprietary telemetry protocols. In thismanner, other external devices may be capable of communicating withprogrammer 24 without needing to establish a secure wireless connection.

IMD 16 and/or programmer 24 may control of the timing of the delivery ofthe first and second stimulation therapies that generate differentphysiological responses to manage urinary or fecal incontinence. Ifexternal programmer 24 controls the stimulation, programmer 24 maytransmit therapy programs for implementation by IMD 16 to IMD 16 viatelemetry module 78. A user (e.g., patient 14 or a clinician) may selectthe first and second stimulation therapy programs from a list providedvia a display of user interface 74. Alternatively, external programmer24 may transmit a signal to IMD 16 indicating that IMD 16 should executelocally stored programs or therapy routines. In such a manner, controlover the electrical stimulation may be distributed between IMD 16 andexternal programmer 24, or may reside in either one alone.

In one example, patient 14 may control the stimulation therapy deliveredby IMD 16 via external programmer 24. For example, patient 14 mayinitiate or terminate delivery of either the first or second stimulationtherapies by IMD 16 via external programmer 24. For example, patient 14may selectively control the delivery of the second stimulation therapyby IMD 16 through input entered via user interface 74. That is, IMD 16may deliver second stimulation therapy based on patient input enteredvia user interface 74. In this way, patient 14 may use programmer 24 todeliver the second stimulation therapy “on demand,” such as when patient14 senses the onset of a leakage episode.

In another example, programmer 24 may present a notification indicativeof the prospective delivery of the second stimulation therapy to patient14 via user interface 74. As an example, prior to delivering the secondstimulation therapy, processor 70 of programmer 24 may generate andpresent a notification that indicates the second stimulation therapywill be delivered within an indicated period of time. IMD 16 may providean indication to programmer 24 via the respective telemetry modules 58,76 that IMD 16 intends on delivering the second stimulation therapy.Programmer 24 may alert patient 14 by presenting a warning message on adisplay of user interface 74, emitting an audible alert, or generating asomatosensory alert (e.g., a vibrating housing). In such an example,programmer 24 may prompt patient 14 for input via a display of userinterface 74. Patient 14 may enter input via user interface 74 thateither confirms delivery of the second stimulation therapy or input formanually aborting the second stimulation therapy. In either case, thepatient input is transmitted to IMD 16 via telemetry module 78.

As previously indicated, programmer 24 may provide a notification topatient 14 when the second stimulation therapy is triggered toofrequently, which may indicate that bladder 12 (FIG. 1) is full.Processor 70 may implement any suitable criteria to generate the alert.Processor 70 may monitor the frequency of the delivery of the secondstimulation therapy by IMD 16, e.g., by receiving input from IMD 16indicating the times at which the second stimulation therapy isdelivered to patient 14 or based on patient input received via userinterface 74, where the patient input controls the delivery of thesecond stimulation therapy. For example, in the event that the secondstimulation therapy is triggered five times within five minutes,processor 50 may generate a notification to patient 14 indicating thesame. This may allow patient 14 to proceed to a bathroom before aleaking episode occurs. The notification provided by programmer 24 mayalso direct patient 14 to locate a restroom and voluntarily void.

Patient 14 may indicate an intent to void via user interface 74, andprocessor 70 may implement a blanking interval through communication ofthe indication to IMD 16 via telemetry module 78. For example, processor70 may transmit a command signal to IMD 16 that indicates IMD 16 shouldtemporarily suspend delivery of the second stimulation therapy. In somecases, this may permit voluntary voiding by patient 14. In someexamples, the length of time for a voiding event may be determined bypressing and holding down a button of user interface 74 for the durationof a voiding event, pressing a button a first time to initiate voidingand a second time when voiding is complete, or based on a predeterminedperiod of time following the indication of voluntary voiding provided bypatient 14. In each case, programmer 24 causes IMD 16 to temporarilysuspend the second stimulation therapy, and, in some cases, the firststimulation therapy, so that voluntary voiding is possible.

In other examples, IMD 16 may automatically determine when patient 14 isattempting to voluntary void, e.g., based on a voiding signature of anEMG signal indicative of bladder activity or based on bladder pressureor contraction. In such examples, IMD 16 may automatically suspend thedelivery of either or both the first and second stimulation therapies topermit patient 14 to voluntary void. In some cases, suspension ofstimulation by IMD 16 is not necessary to facilitate voiding, andstimulation may occur substantially simultaneously with the voluntaryvoiding. For example, the bladder volume will eventually increase to alevel to trigger strong bladder contractions that prevails over thesecond stimulation therapy to allow voiding.

Power source 78 delivers operating power to the components of programmer24. Power source 78 may include a battery and a power generation circuitto produce the operating power. In some examples, the battery may berechargeable to allow extended operation. Recharging may be accomplishedby electrically coupling power source 78 to a cradle or plug that isconnected to an alternating current (AC) outlet. In addition oralternatively, recharging may be accomplished through proximal inductiveinteraction between an external charger and an inductive charging coilwithin programmer 24. In other examples, traditional batteries (e.g.,nickel cadmium or lithium ion batteries) may be used. In addition,programmer 24 may be directly coupled to an alternating current outletto power programmer 24. Power source 78 may include circuitry to monitorpower remaining within a battery. In this manner, user interface 74 mayprovide a current battery level indicator or low battery level indicatorwhen the battery needs to be replaced or recharged. In some cases, powersource 78 may be capable of estimating the remaining time of operationusing the current battery.

FIGS. 5-10 are flow diagrams illustrating example techniques to reducethe likelihood of incontinence events with a therapy system thatgenerates and delivers first stimulation therapy that generates a firstphysiological response by patient 14 and a second stimulation therapythat generates a second physiological response. The first stimulationtherapy may be delivered in as part of open loop therapy that does notuse feedback from a sensor to trigger therapy delivery, while the secondstimulation therapy is delivered as part of closed loop therapy thatutilizes patient input or feedback from a sensor to trigger therapydelivery. The flow diagrams shown in FIGS. 5-10 include some of the samesteps, which are like-numbered for ease of description. The exampletechnique shown in FIGS. 6-10 may be viewed as specific examples of thetechnique shown in FIG. 5.

FIG. 5 is a flow diagram illustrating an example technique fordelivering first and second stimulation therapies to a patient to managefecal or urinary incontinence. IMD 16 delivers first stimulation therapyto patient 14 (100). In some examples, IMD 16 initiates the delivery ofthe first stimulation therapy upon activation of chronic therapydelivery by the clinician. IMD 16 delivers the first stimulation therapychronically, e.g., periodically for an extended period of time, such ashours, days, weeks, or, in examples in which the first and secondstimulation therapies are not delivered simultaneously, until an eventoccurs that triggers delivery of the second stimulation therapy.

IMD 16 monitors a patient condition via a sensor to determine whether atrigger event is detected (102). Example trigger events may be detectedinclude, but are not limited to, bladder contraction exceeding (e.g.,greater than or equal to) a threshold level, abnormal detrusor muscleactivities (e.g., as indicated by an EMG) patient activity levelexceeding a threshold level, patient posture state, and patient input.As previously described, IMD 16 may monitor bladder impedance, bladderpressure, pudendal or sacral afferent nerve signals, a urinary sphincterEMG, or any combination there of to detect changes in bladdercontraction.

The steps of delivering the first stimulation therapy and monitoring thepatient to detect a trigger event are illustrated in FIG. 5 as beingsequential, but it should be understood that these steps may beperformed simultaneously instead of sequentially. As an example, IMD 16may deliver the first stimulation therapy to patient 14 for an extendedperiod of time. During the extended period of time, IMD 16 mayperiodically monitor patient 14 to detect a trigger event. In someexamples, IMD 16 may monitor patient 14 following delivery of a train offirst stimulation therapy, e.g., in examples in which the firststimulation therapy is defined by a plurality of consecutive trains ofstimulation separated by intervals of time. In other examples, IMD 16may monitor patient 14 more frequently or less frequently. In yet otherexamples, IMD 16 may monitor patient 14 substantially continuously.

If IMD 16 does not detect a trigger event (“NO” branch of block 102),IMD 16 continues to deliver the first stimulation therapy (100). On theother hand, if IMD 16 detects a trigger event (“YES” branch of block102), IMD 16 delivers the second stimulation therapy (104). The firstand second stimulation therapies may be delivered substantiallysimultaneously or in an alternating manner (e.g., one type ofstimulation is delivered at a time).

In some examples, IMD 16 delivers the second stimulation therapy for apredetermined period of time, e.g., about 10 seconds to about 50seconds. The duration of the predetermined period of time may beselected such that an imminent involuntary voiding event is suppressed.As described in further detail below with reference to FIG. 9, in someexamples, after the predetermined period of time, IMD 16 determineswhether the patient condition that triggered the delivery of the secondstimulation therapy is still present. For example, IMD 16 may determinewhether the bladder contractions are still greater than or equal to athreshold value. If the patient condition that triggered the delivery ofthe second stimulation therapy is still present, IMD 16 may deliver thesecond stimulation therapy again for another predetermined period oftime.

In other examples, IMD 16 delivers the second stimulation therapy for aperiod of time controlled by patient 14. For example, patient 14 maycontrol the duration of the second stimulation therapy by interactingwith programmer 24, e.g., by pressing a “boost” button on a keypad or atouch screen, or by interacting directly with IMD 16 (e.g., by tappingskin superior to the implanted IMD 16). A maximum therapy period forpatient controlled stimulation may be approximately 3 minutes, althoughother time ranges are contemplated.

After completion of the delivery of the second stimulation therapy, IMD16 reverts back to delivering the first stimulation therapy (100) andthe technique shown in FIG. 5 are repeated as necessary. Thus, IMD 16delivers the first stimulation therapy and, when triggered, delivers thesecond stimulation therapy for a limited duration of time (e.g., shorterin duration than the duration of time that the first stimulation therapyis delivered). That is, IMD 16 delivers chronic stimulation for anextended period of time via the first stimulation therapy, and, whennecessary or desirable, delivers an additional boost of stimulation viathe second stimulation therapy. The boost of stimulation is provided fora comparatively short period of time within the extended period of timeduring which the chronic therapy delivery is provided.

In this way, IMD 16 provides responsive stimulation to control urinaryincontinence. Delivering the second stimulation therapy upon detectionof a trigger event, rather than on a substantially regular basis, mayhelp reduce muscle fatigue by limiting the amount of the secondstimulation therapy provided to patient 14. In addition, implementingthe second stimulation therapy only when needed may help conserve powerof power source 60 of IMD 16. Conserving power may help elongate theuseful life of IMD 16.

FIG. 6 is a flow diagram illustrating an example technique fordelivering a first stimulation therapy to manage incontinence of patient14 and, when triggered by sensed bladder contraction, delivering asecond stimulation therapy to patient 14 to provide an additionalmechanism resulting in a different physiological effect that furtherhelps prevent an involuntary voiding event. The technique shown in FIG.6 allows patient 14 to manually abort the delivery of the secondstimulation therapy. In the description of FIG. 6, bladder contractionsare referred to as the trigger event for activating the delivery of thesecond stimulation therapy. In other examples, the trigger event may beany suitable trigger event, such as the detection of patient input, aparticular patient posture state, a patient activity level greater thanthreshold value, or detrusor muscle activities greater than or equal toa threshold value or substantially matching a template.

As with the technique shown in FIG. 5, processor 50 of IMD 16 controlstherapy delivery module 52 to generate and deliver the first stimulationtherapy to patient 14 (100). Processor 50 monitors a physiologicalparameter of patient 14 to detect bladder contraction (112). Forexample, processor 50 may monitor bladder impedance with the aid ofsignals generated by impedance module 54, or bladder pressure, pudendalor sacral afferent nerve signals, a urinary sphincter EMG, or anycombination thereof with the aid of signals generated by sensor 22.

If processor 50 of IMD 16 does not detect bladder contractions that aregreater than or equal to a threshold level (“NO” branch of block 112),IMD 16 continues to deliver the first stimulation therapy (100). On theother hand, if processor 50 determines that sensed bladder contractionsare indicative of an imminent voiding event or at least an increasedprobability of an occurrence of an involuntary voiding event (e.g., asindicated by a bladder contraction greater than or equal to a thresholdlevel) (“YES” branch of block 112), processor 50 generates anotification for patient 14 (114). The notification may indicate thatbladder contraction indicative of an imminent involuntary voiding eventhas been detected. IMD 16 may alert patient 14 by, for example,wirelessly communicating with programmer 24 to cause programmer 24 toprovide an alert. Programmer 24 may alert the patient by displaying awarning message within a display or emitting an alert sound. In otherexamples, IMD 16 may generate the patient notification by generating asomatosensory alert (e.g., by generating a notification that is felt bypatient 14). For example, IMD 16 may cause an outer housing of IMD 16 tovibrate.

After notifying patient 14 (114), IMD 16 determines whether patient 14has indicated that the second stimulation therapy should be aborted(116) prior to actually delivering the second stimulation therapystimulation. In some examples, IMD 16 may determine if patient 14 wantsto manually abort the delivery of the second stimulation therapy basedon patient input. The patient input may be input entered via programmer24. As an example, patient 14 may press a button on a keypad or selectan icon using a touch screen to enter input. Programmer 24 wirelesslytransmits the patient input to IMD 16. As another example, patient 14may provide input by tapping the skin proximate IMD 16 in apredetermined pattern, such that IMD 16 detects the movement (e.g., viaa signal generated by a motion sensor) and characterizes the movement aspatient input.

When the patient input indicates that patient 14 wants to stop thedelivery of the second stimulation therapy (“YES” branch of block 116),IMD 16 continues to deliver the first stimulation therapy (100). Patient14 may want to abort the delivery of the second stimulation therapy, forexample, during a voluntary voiding event. Permitting patient 14 tomanually abort the delivery of second stimulation therapy may also allowpatient 14 to prevent unwanted stimulation in the event that IMD 16incorrectly detected the bladder contraction.

If processor 50 of IMD 16 determines that patient 14 does not want tomanually abort the delivery of the second stimulation therapy (“NO”branch of block 116), IMD 16 delivers the second stimulation therapy fora therapy period, which may be predetermined (104). Processor 50 mayautomatically determine that patient 14 does not want to manually abortthe delivery of the second stimulation therapy by receiving input frompatient 14 indicating that the second stimulation therapy is desirable.In other examples, processor 50 automatically determines that patient 14does not want to manually abort the delivery of the second stimulationtherapy if patient 14 does not provide any input within a certain periodof time following the patient notification. After IMD 16 delivers thesecond stimulation therapy for a therapy period (104), IMD 16 continuesto deliver the first stimulation therapy (100).

FIG. 7 is a flow diagram illustrating an example technique fordelivering a stimulation therapy to patient 14 to manage urinary orfecal incontinence, where the technique includes delivering a first,primary electrical stimulation therapy and, upon receiving patientinput, delivering a second stimulation therapy. The example techniqueshown in FIG. 7 is an example of the technique shown in FIG. 5. That is,the event that triggers the delivery of the second stimulation therapyin FIG. 7 is patient input.

In accordance with the technique shown in FIG. 7, IMD 16 delivers firststimulation therapy to patient 14 (100). Upon receiving patient input(122), processor 50 of IMD 16 controls therapy delivery module 52 togenerate and deliver the second stimulation therapy to patient 14 togenerate the second physiological response that helps prevent aninvoluntary voiding event. In some cases, processor 50 of IMD 16 uponreceiving patient input to discontinue the delivery of the firststimulation therapy prior to the delivery of the second stimulationtherapy, while in other examples the first and second stimulationtherapies are delivered substantially simultaneously.

As previously indicated, patient 14 may provide the patient input viaprogrammer 24, e.g., by activating a button on a keypad or select anicon using a touch screen of programmer 24. Programmer 24 wirelesslycommunicates the patient input to IMD 16. In other examples, patient 14may provide input indicating the delivery of the second stimulationtherapy is desirable via IMD 16. For example, IMD 16 may include amotion sensor that detects movement of IMD 16 and patient 14 may provideinput by tapping the skin proximate IMD 16 in a predetermined pattern,such that IMD 16 detects the movement and characterizes the movement aspatient input.

If IMD 16 does not receive patient input that activates the delivery ofthe second stimulation therapy (“NO” branch of block 122), IMD 16continues to deliver the first stimulation therapy (100) and monitor forpatient input.

FIG. 8 is a flow diagram illustrating an example technique forcontrolling the delivery of the second stimulation therapy to patient14, and notifying patient 14 when the second stimulation therapy isdelivered too frequently. As with the techniques shown in FIGS. 5-7, IMD16 first delivers a first stimulation therapy to patient 14 (100). Inaccordance with the previously described example methods, IMD 16monitors a patient parameter (e.g., a physiological parameter, activitylevel or posture state) and/or patient input to detect a trigger event(102).

If IMD 16 does not detect a trigger event (“NO” branch of block 102),IMD 16 continues to deliver the first stimulation therapy (100).However, if IMD 16 detects a trigger event (“YES” branch of block 102),IMD 16 determines whether too many trigger events occurred within apredetermined interval (134). In the example shown in FIG. 8, processor50 of IMD 16 compares the number of trigger events detected within the apredetermined interval to a threshold value, which may be stored inmemory 56 (FIG. 3) of IMD 16.

If processor 50 determines that too many trigger events occurred withinthe predetermined interval of time (“YES” branch of block 134),processor 50 generates an alert to notify patient 14 that the triggerevents that activate the delivery of the second stimulation therapy areoccurring too frequently (138). Trigger events occurring at a frequencyhigher than a stored frequency may indicate that bladder 12 (FIG. 1) isfull. Processor 50 (or processor 70 of programmer 24) may track thenumber of trigger events within the predetermined range of time usingany suitable technique, such as by implementing a counter.

If processor 50 determines that too many trigger events have notoccurred within the predetermined interval of time (“NO” branch of block134), IMD 16 delivers the second stimulation therapy stimulation topatient 14 (104) and repeats the technique shown in FIG. 8 as necessary.

FIG. 9 is a flow diagram illustrating another example technique fordelivering first stimulation therapy to manage incontinence and, whentriggered by sensor or patient input, delivering a second stimulationtherapy to boost the effectiveness of the first stimulation therapy. Inthe example technique illustrated in FIG. 9, the second stimulationtherapy is delivered for another therapy period if a trigger event isstill detected after the stimulation therapy was delivered for a therapyperiod. Each therapy period may include the delivery of stimulationsignals for a predetermined duration of time. In the technique shown inFIG. 9, IMD 16 delivers the second stimulation therapy until the triggerevent is no longer detected or the therapy interval is over.

IMD 16 first delivers the first stimulation therapy to patient 14 (100)and monitors patient 14 to detect a trigger event (102). If IMD 16 doesnot detect a trigger event (“NO” branch of block 102), IMD 16 continuesdeliver the first stimulation therapy (100) until a trigger event isdetected. Upon detecting the trigger event (“YES” branch of block 102),IMD 16 delivers the second stimulation therapy stimulation to patient 14(104). In the example shown in FIG. 9, IMD 16 delivers the secondstimulation therapy to patient 14 by delivering a plurality ofstimulation signals during a predetermined range of time, which may bereferred to as a therapy period.

After delivering the second stimulation therapy for the therapy period,IMD 16 determines whether the trigger event is detected again or isstill occurring (146). In an example in which the trigger event iscontraction of bladder 12 of patient 14, IMD 16 determines whether thecontraction of bladder 12 is greater than or equal to a threshold level.If the bladder contraction subsided during the first therapy period(“NO” branch of block 146), IMD 16 deactivates delivery of the secondstimulation therapy and reverts back to delivering the first stimulationtherapy (100) and monitoring the patient for another trigger event(102). On the hand, if processor 50 of IMD 16 redetects the triggerevent (“YES” branch of block 146), IMD 16 continues to deliver thesecond stimulation therapy for a second therapy period (104).

After the second therapy period, processor 50 determines whether thetrigger event is still present (146), and continues to control therapydelivery module 52 (FIG. 3) deliver the second stimulation therapy untilthe trigger event is no longer present. In other examples, processor 50controls therapy delivery module 52 to deliver the second stimulationtherapy until the trigger event is no longer present or until a maximumnumber of therapy periods have been delivered within a certain amount oftime. The maximum number of therapy periods within certain amount oftime may be stored in memory 56 of IMD 16 or another device, and may beselected by a clinician.

FIG. 10 is a flow diagram illustrating an example technique fordelivering first stimulation therapy and, when triggered by sensor inputor patient input, delivering adaptive second stimulation therapy to apatient. Adaptive second stimulation therapy includes second stimulationtherapy that generates a different physiological response than the firststimulation therapy, whereby the stimulation parameters of the secondstimulation therapy changes over time. Adaptive second stimulationtherapy may be configured to maximize closure of the urinary or analsphincter and minimize muscle fatigue.

IMD 16 delivers first stimulation therapy to patient 14 (100) andmonitors signals from one or more sensors and/or patient input to detecttrigger events (102). If processor 50 of IMD 16 does not detect atrigger event (“NO” branch of block 102), IMD 16 continues to deliverthe first stimulation therapy. However, if processor 50 detects atrigger event (“YES” branch of block 102), IMD 16 determines whether thesecond stimulation therapy, which is a temporary “dose” of stimulationtherapy, was previously delivered within a predetermined interval oftime (154). The predetermined interval of time may be referred to as aninter-therapy interval and may be, for example, approximately 30seconds, although other intervals of time are contemplated.

If IMD 16 has not previously delivered the second stimulation therapywithin the interval of time (“NO” branch of block 154), IMD 16 deliversthe second stimulation therapy to patient 14 without modifying thetherapy parameters of the second stimulation therapy (104). On the otherhand, if processor 50 of IMD 16 determines that IMD 16 has previouslydelivered the second stimulation therapy within the interval of time(“YES” branch of block 154), processor 50 controls therapy deliverymodule 52 (FIG. 3) to generate and deliver adaptive second stimulationtherapy to patient 14 (158). Processor 50 adjusts one or more parametersof the second stimulation therapy if IMD 16 has previously delivered thesecond stimulation therapy within the interval of time, therebyproviding “adaptive” second stimulation therapy. Adjusting one or moreparameters of the second stimulation therapy help minimize patientadaptation to the second stimulation therapy, as well as any musclefatigue that may result from the second stimulation therapy.

In general, changing one or more aspects of the second stimulationtherapy if IMD 16 has previously delivered the second stimulationtherapy within the predetermined interval of time may help prevent thesame stimulation signal from being delivered to patient 14 for arelatively long period of time. This helps prevent patient 14 fromgrowing accustomed to the stimulation signal, e.g., adaptation, whichmay result in a decrease in the effectiveness of the second stimulationtherapy over time. In addition, changing one or more aspects of thesecond stimulation therapy may help reduce muscle fatigue by changingthe way in which the muscles of patient 14 are stimulated by the secondstimulation therapy.

IMD 16 delivers the adaptive second stimulation therapy (158) bydelivering the second stimulation therapy according to differentparameters than then previously delivered the second stimulationtherapy. As an example, IMD 16 may deliver adaptive second stimulationtherapy by delivering second stimulation therapy that stimulatesfast-twitch muscles during a first therapy period, and the secondstimulation therapy that stimulates slow-twitch muscles during a secondtherapy period subsequent to the first therapy period, and varying theduration of the first and second intervals over time each time thatadaptive second stimulation therapy is delivered within thepredetermined interval. Example stimulation signals that illustrateadaptive second stimulation therapy is described with respect to FIGS.13A-14C.

While the techniques described with reference to FIGS. 6-10 areprimarily described as being performed by processor 50 of IMD 16, inother examples, processor 70 of programmer 24 or a processor of anothercomputing device may perform any part of the techniques in FIGS. 5-10 orany other technique described herein. In addition, any of the techniquesshown in FIGS. 5-10 for controlling the delivery of stimulation therapyto patient 14 to manage incontinence may be used in combination witheach other.

FIG. 11 illustrates an example stimulation signal 200 that therapydelivery module 52 of IMD 16 may generate and deliver as part of thesecond stimulation therapy. Stimulation signal 200 includes stimulationpulses 202 and stimulation pulses 204. In the example shown in FIG. 11,stimulation pulses 202 are delivered over an interval that has durationT₁ and stimulation pulses 204 are delivered over an interval that hasduration T₂. Stimulation pulses 202 are delivered at a higher frequencythan stimulation pulses 204. The high frequency stimulation pulses 202may be designed to maximize closure of the urinary sphincter or bladderoutlet while the low frequency stimulation pulses 204 may be designed tominimize muscle fatigue. By alternating the delivery of the high and lowfrequency stimulation pulses 202, 204, respectively, the secondstimulation therapy may be configured to reduce muscle fatigue whileminimizing the possibility of an occurrence of an involuntary voidingevent.

As previously indicated, IMD 16 may deliver the second stimulationtherapy for a predetermined therapy period. In some examples, during thetherapy period, IMD 16 may provide the first stimulation therapy topatient 14 by delivering stimulation pulses 202 at a frequency ofapproximately 40 Hz to approximately 66 Hz for a duration ofapproximately 10 seconds to 20 seconds, and subsequently deliverstimulation pulses 204 at a frequency of approximately 30 Hz for aduration of approximately 10 seconds to approximately 20 seconds. Otherstimulation parameters are contemplated.

Additionally, although the stimulation pulses of stimulation signal 200,i.e., relatively high frequency stimulation pulses 202 and relativelylow stimulation pulses 204, are shown in FIG. 11 as a continuous trainof pulses, stimulation pulses may also be delivered in otherconfigurations, such as bursts of pulses. For example, one or both ofstimulation pulses 202 and 204 may be delivered as bursts of pulses. Thebursts of pulses may be controlled, for example, by selecting duty cyclevalues, e.g., approximately 50% ON/50% OFF, approximately 30% ON/70%OFF, or approximately 20% ON/80% OFF.

FIG. 12 illustrates example stimulation signals 210A and 210B thattherapy delivery module 52 of IMD 16 may generate and deliver as part ofthe second stimulation therapy. Stimulation signal 210A includes burstsof relatively high frequency stimulation pulses 212A and relatively lowfrequency stimulation pulses 214A. Stimulation signal 210B includesbursts of relatively high frequency stimulation pulses 212B andrelatively low frequency stimulation pulses 214B. In the example shownin FIG. 12, stimulation signals 210A and 210B are similar to stimulationsignal 200 shown in FIG. 11 and, thus, are also similar to each other.

As shown in FIG. 12, IMD 16 does not deliver stimulation during theinter-therapy interval, T_(INT), following the delivery of stimulationsignal 210A. IMD 16 delivers stimulation signal 210B at the expirationof the inter-therapy interval T_(INT). By not delivering stimulationduring T_(INT), muscle fatigue may be minimized in comparison todelivering stimulation substantially continuously during a therapyinterval. An inter-therapy interval, such as T_(INT), may beapproximately 10 seconds in some examples. In other examples, aninter-therapy interval may be more or less than 10 seconds. In any case,the purpose of an inter-therapy interval is to deliver no or minimalstimulation so as to minimize muscle fatigue.

FIGS. 13A-13C illustrate example stimulation signals that IMD 16 maydeliver as part of the second stimulation therapy in an adaptive fashionso as to minimize muscle fatigue. In particular, FIGS. 13A-13Cillustrate example stimulation signals 220, 230, and 240, respectively.Stimulation signals 220, 230, and 240 may be delivered sequentially. Inparticular, stimulation signals 230 and 240 may be delivered within aninter-therapy interval (e.g., about 30 seconds) of the previousstimulation signal that was delivered as part of the second stimulationtherapy. That is stimulation signal 230 may be delivered afterexpiration of the inter-therapy interval that began after delivery ofstimulation signal 220 and stimulation signal 240 may be delivered afterexpiration of the inter-therapy interval that began after delivery ofstimulation signal 230.

As discussed with respect to FIG. 10, in some examples, processor 50adjusts one or more parameters of the second stimulation therapy if IMD16 has previously delivered the second stimulation therapy within theinterval of time. Adjusting one or more parameters of the secondstimulation therapy help minimize patient adaptation to the secondstimulation therapy, as well as any muscle fatigue that may result fromthe second stimulation therapy. FIGS. 13A-13C provide an example ofadaptive second stimulation therapy in which, for each subsequentstimulation signal triggered within an inter-therapy interval of theprevious second stimulation therapy delivery period, the duration offast-twitch muscle stimulation decreases by a predetermined amount,e.g., five seconds.

In FIGS. 13A-13C the stimulation pulses that stimulate fast-twitchmuscles are the stimulation pulses of relatively high frequency, i.e.,bursts 222, 232, and 242. As shown in FIGS. 13B and 13C, the timeinterval 233 for stimulation pulses 232 has decreased in comparison tothe time interval 223 for stimulation pulses 222, and the time interval243 for stimulation pulses 242 has decreased in comparison to timerinterval 233 for stimulation pulses 232. Accordingly, the time interval235 for relatively low frequency stimulation pulses 234 has increased incomparison to the time interval 225 for relatively low frequencystimulation pulses 224, and the time interval 245 for relatively lowfrequency stimulation pulses 244 has increased in comparison to timerinterval 235 for stimulation pulses 234.

Because the time interval for the high frequency stimulation pulsesdecreases and the time interval for the low frequency stimulation pulsesincreases for each subsequent stimulation signal, the duration of timethat the fast twitch muscles are activated is minimized, which may helpminimize muscle fatigue.

FIGS. 14A-14C illustrate another set of example of stimulation signalsIMD 16 may generate and deliver as part of adaptive stimulation therapyto help minimize muscle fatigue. In particular, FIGS. 14A-14C illustrateexample stimulation signals 250, 260, and 270, respectively. As with theexample stimulation signals shown in FIGS. 13A-13C, stimulation signals250, 260, and 270 may be delivered sequentially, e.g., such that signal260 is delivered subsequent to signal 250, and signal 270 is deliveredsubsequent to signal 260.

Signals 250, 260, and 270 in FIGS. 14A-14C are also similar to thesignals in FIGS. 13A-C in the sense that, for each subsequent signal,the number of high frequency stimulation pulses decreases and the numberof low frequency stimulation pulses increases. However, the manner inwhich processor 50 of IMD 16 adjusts the signals 250, 260, and 270 overtime is different than that for signals 220, 230, and 240. Specifically,for each subsequently delivered signal, a first portion of therelatively high frequency stimulation pulses is replaced with relativelylow frequency stimulation pulses compared to the previous signal.

In FIGS. 14A-14C, T₁ defines an interval during which bursts ofrelatively high frequency stimulation pulses are delivered duringdelivery of standard second stimulation therapy, i.e., non-adaptivesecond stimulation therapy. Interval T₂ defines an interval during whichrelatively low frequency stimulation pluses are delivered for bothnon-adaptive and adaptive second stimulation therapy. When processor 50modifies the stimulation signals to provide adaptive second stimulationtherapy, processor 50 replaces, for each subsequent signal, a firstportion of the high frequency stimulation pulses with low frequencystimulation pulses. The time interval within T₁ during which processor50 delivers low frequency stimulation pulses is labeled T₃.

Accordingly, stimulation signal 250 in FIG. 14A includes relatively highfrequency stimulation pulses 252 during interval T₁, and relatively lowfrequency stimulation pulses during interval T₂. Example stimulationsignal 260 in FIG. 14B represents an adapted stimulation signaldelivered subsequent to signal 250. Signal 260 includes relatively lowfrequency stimulation pulses 266 that precede the relatively highfrequency stimulation pulses 262 during interval T₁. Relatively lowfrequency stimulation pulses 266 are delivered over interval T₃ withininterval T₁. If processor 50 determines that another therapy period ofthe second stimulation therapy is desirable after signal 260 isdelivered to patient 14, processor 50 may further adapt stimulationsignal 260.

In the example shown in FIG. 14C, processor 50 modifies stimulationsignal 260 such that relatively low frequency stimulation pulses 276,which precede relatively high frequency stimulation pulses 272 duringinterval T₁, are delivered for approximately twice as long as therelatively low frequency stimulation pulses 266 that precede therelatively high frequency stimulation pulses 262 in stimulation signal260. That is, the duration of interval T₃ for stimulation signal 270 isapproximately twice the duration of interval T₃ for stimulation signal260. Interval T₃ may generally be selected to have an initial value andto increase for each subsequent adaptive stimulation signal by thatinitial value. In this way, T₃ increases in a way that may alloweffective therapy to be delivered while minimizing muscle fatigue. Theinitial value of interval T₃ may be a fraction of interval T₁ and, moreparticularly, may be selected to allow a number of adaptive stimulationsignal to be delivered before the value of T₃ approaches the value ofT₁. Other values for T₃ and algorithms for modifying the value of T₃ fordelivering adaptive stimulation are contemplated.

Although not shown in FIGS. 14A-14C, in some examples, this adaptivepattern may continue for subsequently delivered stimulation pulses untillow frequency stimulation pulses have replaced all relatively highfrequency stimulation pulses during interval T₁, or, in other words,until the interval T₃ equals interval T₁. In such examples, anysubsequently delivered stimulation pulses may include only low frequencystimulation pulses. In other examples, however, processor 50 maycontinue to adjust the stimulation signal, but maintain at least somerelatively high frequency stimulation signals to activate the fasttwitch muscle fibers. Processor 50 may reset the adaptive pattern ofstimulation signals after a certain period of time of not triggering thesecond stimulation therapy. That is, processor 50 may deliver the secondstimulation in an adaptive fashion when the second stimulation istriggered within a therapy interval, and continue to deliver secondstimulation in an adaptive fashion as long as the second stimulation istriggered within consecutive therapy intervals. However, when secondstimulation therapy is not triggered during a therapy interval,processor 50 may reset the adaptive pattern so that the next time secondstimulation therapy is delivered in accordance with a non-adaptedsignal, e.g., signal 250.

The example stimulation signals shown in FIGS. 13A-13C and 14A-14C aremerely examples. The purpose of these signals is to provide workingexamples to demonstrate the described techniques for providing twodifferent types of stimulation therapy to manage patient incontinence.

In some cases, patient 14 may perceive the delivery of the secondstimulation therapy or the transition from the delivery of the firststimulation therapy to the delivery of the second stimulation therapy,e.g., when the first and second stimulation therapies are delivered atdifferent times (e.g., in a non-overlapping manner). Because thestimulation signals associated with the second stimulation therapy mayhave a higher intensity (e.g., a higher amplitude or frequency) than thestimulation signals associated with the first stimulation therapy, theinitiation of the second stimulation therapy may cause discomfort topatient 14. The discomfort may or may not exceed a pain threshold ofpatient 14.

In order to help minimize the discomfort to patient 14 from the deliveryof the second stimulation therapy or the transition from the firststimulation therapy to the second stimulation therapy, processor 50 ofIMD 16 (FIG. 3) or a processor of another device (e.g., programmer 24)may control therapy module 52 (FIG. 3) of IMD 16 to gradually modify oneor more stimulation parameter values (e.g., amplitude or frequency) overtime, rather than abruptly (e.g., instantaneously) increase theparameter values relative to the one or more stimulation parametervalues defined by the first stimulation therapy. That is, upondetermining that delivery of the second stimulation therapy isdesirable, e.g., in response to a sensed physiological condition orpatient input, processor 50 of IMD 16 (or another device) may controltherapy delivery module 52 to deliver therapy to patient 14 by graduallytransitioning between the one or more stimulation parameter values ofthe first stimulation therapy to the one or more stimulation parametervalues of the second stimulation therapy. In some examples, thetransition from the first stimulation therapy delivery to the secondstimulation therapy includes a ramping up of the amplitude and frequencyof the stimulation signals. The amplitude, frequency or otherstimulation parameter value (e.g., pulse width in the case ofstimulation pulses) may be modified in a linear, nonlinear, exponentialor step-wise manner.

Similarly, upon determining termination of the second stimulationtherapy delivery is desirable (e.g., because of the termination of thetherapy period or because of patient input indicating abortion of thesecond stimulation therapy is desirable), processor 50 (or anotherprocessor) may control therapy delivery module 52 to graduallytransition from therapy delivery according to the one or morestimulation parameter values of the second stimulation therapy to theone or more stimulation parameter values of the first stimulationtherapy. In some examples, the transition from the second stimulationtherapy delivery to the first stimulation therapy includes a rampingdown of the amplitude and frequency of the stimulation signals.

The gradual ramping upward or downward of the one or more stimulationparameter values is contrary to an instantaneous modification to the oneor more stimulation parameter values. An immediate change in astimulation parameter value may be characterized by, for example, a jumpfrom therapy delivery according to a first stimulation parameter valueto therapy delivery according to a second stimulation parameter value.In contrast, a gradual change in the stimulation parameter value may beaccomplished by, for example, shifting from a stimulation parametervalue defined by the first stimulation therapy to therapy deliveryaccording to a second stimulation parameter value defined by the secondstimulation therapy over time. The shift from the first stimulationparameter value to the second stimulation parameter value may involve,for example, therapy delivery according to intermediate stimulationparameter values between the first and second stimulation parametervalues.

Various techniques may be used to transition between stimulationparameter values of the first and second stimulation therapies. In someexamples, processor 50 of IMD 16 (or another device) utilizes apredetermined constant or variable rate of change to gradually ramp upor down between the stimulation parameter values (e.g., the amplitudeand/or frequency) of the first and second stimulation therapies. Inother examples, processor 50 may gradually increase or decrease astimulation parameter value over a predetermined range of time (referredto as a transition time). By gradually adjusting a stimulation parametervalue to a desired level over time rather than making an adjustment to adesired value substantially immediately, IMD 16 may effectively adjustthe stimulation parameter value without patient 14 experiencingundesirable side effects that may result from making abrupt changes to astimulation parameter, such as stimulation amplitude, too quickly.

In some cases, the first and second stimulation therapies definedifferent stimulation signal amplitudes. Processor 50 of IMD 16 (or aprocessor of another device, such as programmer 24) may control therapymodule 52 to shift from the first stimulation therapy to the secondstimulation therapy by gradually shifting from a baseline amplitude(defined by the first stimulation therapy) to a second amplitude(defined by the second stimulation therapy) according to a predeterminedpattern. Example patterns include, but are not limited to, a linear,non-linear or exponential rate of change. That is, processor 50 (oranother processor) may gradually ramp the amplitude up or down using alinear, non-linear or exponential rate of change.

Similarly, in some cases, the first and second stimulation therapiesdefine different stimulation signal frequencies in addition to orinstead of the different amplitudes. Processor 50 of IMD 16 (or aprocessor of another device, such as programmer 24) may control therapymodule 52 to shift from the first stimulation therapy to the secondstimulation therapy by gradually shifting from a baseline frequency(defined by the first stimulation therapy) to a second frequency(defined by the second stimulation therapy) according to a predeterminedpattern. Example patterns include, but are not limited to, a linearpattern, a nonlinear pattern or an exponential pattern. In addition, insome examples, patterns such as a step-wise pattern may be used totransition between stimulation parameter values.

In examples in which the first and second stimulation therapies definedifferent stimulation signal frequencies and different amplitudes,processor 50 of IMD 16 (or another processor) may modify one or both thefrequency and/or amplitude values at a time. For example, if the secondstimulation therapy defines greater amplitude and frequency values thanthe first stimulation therapy, processor 50 may control therapy module52 to gradually increase the stimulation amplitude over time (e.g.,using a predetermined rate of change, as defined by a predeterminedpattern, or over a predetermined duration of time) while maintaining thefrequency defined by the first stimulation therapy. After thestimulation amplitude has reached a second amplitude value defined bythe second stimulation therapy, processor 50 may deliver stimulationtherapy according to the second amplitude value while controllingtherapy module 52 to gradually increase the frequency over time untilthe frequency value of the second stimulation therapy is achieved.

In other examples, processor 50 may control therapy module 52 togradually increase the stimulation signal frequency over time whilemaintaining a first amplitude value defined by the first stimulationtherapy. After the frequency has reached a second frequency valuedefined by the second stimulation therapy, processor 50 may deliverstimulation therapy to patient 14 according to the second frequencywhile controlling therapy module 52 to gradually increase the amplitudeover time until the amplitude value of the second stimulation therapy isachieved.

In other examples in which the first and second stimulation therapiesdefine different stimulation parameter values, processor 50 of IMD 16(or another processor) may modify all of the stimulation parametervalues at the same time. In some cases, one of the stimulation parametervalues is gradually changed over time while another is instantaneouslychanged. For example, upon determining the delivery of the secondstimulation therapy is desirable, processor 50 of IMD 16 (or anotherprocessor) may gradually increase the stimulation amplitude (e.g., usinga predetermined rate of change or over a predetermined duration of time)while applying the frequency of the second stimulation therapy at theonset of the second stimulation therapy delivery. That is, processor 50controls therapy module 52 to shift to the frequency of the secondstimulation therapy immediately upon determining delivery of the secondstimulation therapy is desirable.

In other examples, upon determining the delivery of the secondstimulation therapy is desirable, processor 50 of IMD 16 (or anotherprocessor) may gradually increase the stimulation frequency (e.g., usinga predetermined rate of change, as defined by a predetermined pattern,or over a predetermined duration of time) while applying the amplitudeof the second stimulation therapy at the onset of the second stimulationtherapy delivery. In this way, processor 50 controls therapy module 52to shift to the amplitude value of the second stimulation therapyimmediately upon determining delivery of the second stimulation therapyis desirable.

While techniques for transitioning from the first stimulation therapy tothe second stimulation therapy are described above, similar techniquesmay also be applied to transitioning from the second stimulation therapyto the first stimulation therapy upon determining the termination of thesecond stimulation therapy is desirable. As previously indicated, thefirst stimulation therapy periodically over an extended period of time,e.g., chronic stimulation and the second stimulation therapy isperiodically delivered to patient 14 to provide a short-term boost tothe effectiveness of the first stimulation therapy. Thus, termination ofthe second stimulation therapy may be desirable after a predeterminedtherapy period in which the second stimulation therapy is delivered (inan overlapping or non-overlapping manner with the first stimulationtherapy) or in response to patient input indicating the termination ofthe second stimulation therapy is desirable.

Other techniques may be used to minimize patient comfort resulting fromthe onset of the second stimulation therapy instead or in addition togradually ramping up or down of one or stimulation parameter values whentransitioning between the first and second stimulation therapies. Insome examples, IMD 16 may implement prepulse inhibition in order tominimize the perception of the shift between the stimulation parametervalues of the first stimulation therapy to the increased stimulationparameter values of the second stimulation therapy. Prepulse inhibitionis a neurological phenomenon in which a weaker prestimulus (alsoreferred to as a prepulse) inhibits the reaction of an organism to asubsequent stronger stimulus (e.g., a stimulation signal of the secondstimulation therapy).

FIG. 15 is a conceptual illustration of example stimulation signals thattherapy delivery module 52 of IMD 16 may generate and deliver as part ofthe second stimulation therapy. In the example shown in FIG. 15, the IMD16 delivers prestimulus 280 prior to delivering stimulation signal 200,which generates the second physiological effect (e.g., promotion ofinternal urinary sphincter contraction) associated with the secondstimulation therapy. As described with respect to FIG. 11, in someexamples, stimulation signal 200 includes stimulation pulses 202 andstimulation pulses 204, which have a lower frequency than stimulationpulses. Other stimulation signals may be used instead of or in additionto stimulation signal 200 to provide the second stimulation therapy.

Prestimulus 280 includes one or more stimulation signals (e.g., pulses)that are delivered before each therapy period of the second stimulationtherapy in order to substantiate the central perception inhibitioneffect. In the example shown in FIG. 15, prestimulus 280 includes asingle stimulation pulse that is delivered about 1 ms to about 25 msprior to the delivery of stimulation signal 200. If the secondstimulation therapy is delivered for more than one consecutive therapyperiod, e.g., as described with respect to FIG. 12, processor 50 of IMD16 (or another device) may control therapy module 52 to deliverprestimulus 280 prior to each therapy period.

In general, prestimulus 280 includes one or more stimulation signalshaving a smaller intensity than stimulation signal 200 delivered as partof the second stimulation therapy. Stimulation intensity may be afunction of, e.g., defined by, for example, the amplitude and/orfrequency of a stimulation signal. In the example shown in FIG. 15,prestimulus 280 includes a single stimulation pulse that has anamplitude that is about 0.10 to 0.50 of the amplitude of the stimulationsignals 200. In other examples, IMD 16 can deliver a single prepulse(e.g., as shown in FIG. 15) or a prestimulus train of pulses similar topulse 280 shown in FIG. 15 (e.g., about two to about 100 pulses) topatient 14 before the first stimulation therapy period of a plurality ofconsecutive second stimulation therapy periods, or during a secondstimulation therapy period, rather than before each therapy period asdescribed with respect to FIG. 15.

In addition to or instead of the gradual modification of stimulationparameter values and the prepulse inhibition, electrical nerve block maybe used to minimize discomfort to patient 14 that may result from thedelivery of the second stimulation therapy. For example, IMD 16 maydeliver a relatively high frequency stimulation via one or moreelectrodes 29 (FIG. 3) or a separate set of electrodes to a tissue siteproximal to the target stimulation site for the second stimulationtherapy (e.g., a tissue site closer to the spinal cord than the targetstimulation site) and along the same nerve targeted by the secondstimulation therapy. Electrical nerve block may help block conductionalong the nerve to minimize perception of the delivery of the secondstimulation therapy by patient 14.

The nerve block may be achieved via a high frequency stimulation signalhaving a frequency of about 200 Hz to about 20 kHz, although otherfrequency ranges are contemplated and may be specific to patient 14.Delivery of high frequency nerve block may be useful to initiate arelatively rapid onset of nerve conduction that is temporally correlatedwith the delivery of the second stimulation therapy, thereby providingrelevant nerve conduction block. In some examples, processor 50 of IMD16 (or another device) may control therapy module 52 to initiate thedelivery of the high frequency stimulation to achieve the nerve blockbefore or at the onset of the second stimulation therapy. In someexamples, the high frequency nerve block may be maintained throughoutthe delivery of the second stimulation therapy period. In otherexamples, a device separate from IMD 16 may deliver the stimulation toblock nerve conduction. In addition, nerve block stimulation other thanhigh frequency stimulation, such as anodal block stimulation, may alsobe used.

Other techniques may also be used to minimize discomfort to patient 14that may result from the delivery of the second stimulation therapy inaddition to or instead of the techniques described above. In someexamples, other innocuous stimulation is delivered before or at theonset of the second stimulation therapy. For example, in some examples,an outer housing of IMD 16 vibrates during the second stimulationtherapy period in order to help minimize the discomfort to patient 14.The vibration of outer housing of IMD 16 may produce paresthesia nearthe target tissue site for the second stimulation therapy in examples inwhich IMD 16 is implanted near the target tissue site. IMD 16 mayvibrate at a frequency of about 1 Hz to about 200 Hz, although otherfrequency ranges are contemplated.

In yet other examples, IMD 16 or another device delivers stimulation totissue sites within patient 14 other than the target tissue site for thesecond stimulation therapy in order to minimize the discomfort topatient 14 from the delivery of the second stimulation therapy.Different stimulation frequencies for the delivery of stimulation to therelevant tissue site (which may be internal or external) may elicitdifferent patient responses. For example, a relatively low frequencystimulation may activate muscle tissue and/or reduce pain resulting fromthe second stimulation therapy by stimulating the production ofendogenous endorphins, and a relatively high frequency stimulation mayproduce paresthesia.

In some examples, IMD 16 or another device (e.g., a separatemicrostimulator or external medical device coupled to external orsubcutaneous electrodes) delivers stimulation to a dermatome associatedwith the target nerve for the second stimulation therapy (e.g., ahypogastric nerve, a pudendal nerve, a dorsal penile nerve in a malepatient, a dorsal clitoral nerve in a female patient). A dermatome canbe an area of skin that is supplied by the target nerve. Delivery ofstimulation to the dermatome may, for example, produce paresthesia orproduce endogenous endorphins that help reduce pain perceived by patient14. In examples in which IMD 16 delivers the stimulation to thedermatome, IMD 16 can deliver the stimulation to the dermatome usingselect electrodes of a lead that is separate from the lead (e.g., lead28 in FIG. 1) that delivers the second stimulation therapy to patient14.

As another example, for female patients, a vaginal plug can be used todeliver stimulation during the second stimulation therapy period inorder to help minimize the discomfort to patient 14, e.g., by producingparesthesia. If a device separate from IMD 16 is used to deliver thestimulation to patient 14 that is used to minimize discomfort to patient14, the separate device may be external or implanted within patient 14,and may communicate with IMD 16 via a wired connection or a wirelesscommunication technique (e.g., RF communication techniques).

The techniques described in this disclosure may reduce or substantiallyeliminate leaking episodes caused by urinary incontinence. That is, bydelivering first stimulation therapy to modulate nerve afferentactivities to inhibit bladder contraction, or to maintain internalurinary sphincter closure or urethral closure and, when triggered,second stimulation therapy configured to maximize closure of theinternal urinary sphincter, external urinary sphincter, and/or theperiurethral muscles, improved management of urinary incontinence may beachieved. The techniques described above may also provide advantageousfeatures that allow a patient to control the delivery of the secondstimulation therapy. For example, the patient may actively triggerdelivery of the second stimulation therapy or may manually abort thesecond stimulation therapy. The patient may also temporarily inhibit ordeactivate the second stimulation therapy when voiding voluntarily.

The techniques described in this disclosure may reduce or substantiallyeliminate leaking episodes caused by fecal incontinence. In fecalincontinence examples, the IMD may deliver first stimulation therapy to,for example, a sacral nerve to improve internal and/or external analsphincter muscle tone, and deliver second stimulation therapy to, forexample, a sacral nerve, an internal sphincter, or an externalsphincter. The first stimulation therapy may help to close or maintaininternal sphincter closure or improve internal and/or external analsphincter muscle tone. The second stimulation therapy may promotecontraction of the internal anal sphincter and/or the external analsphincter.

Similar to the therapy techniques described with respect to urinaryincontinence, the first stimulation therapy may be delivered on aregular basis, e.g., to improve muscle tone, and the second stimulationtherapy may be viewed as a short term boost to the effectiveness of thefirst stimulation therapy or to close or promote closure of the internaland/or external anal sphincter. The second stimulation therapy may bedelivered in response to detecting a trigger event, such as receivingpatient input, detecting a patient parameter indicative of an imminentfecal incontinence event, or detecting a patient parameter indicative ofan increased probability of a fecal incontinence event. Example patientparameters may include contraction of the anal sphincter, patientactivity level, or patient posture state. The IMD may detect contractionof the anal sphincter using a pressure sensor, an EMG sensor, or anyother suitable sensing mechanism.

In some examples, the disclosure is directed to a a method comprisingdelivering, with a medical device, first electrical stimulation therapyto a patient to generate a first physiological effect, receiving inputfrom the patient or a sensor while the medical device is delivering thefirst electrical stimulation therapy, and delivering, with the medicaldevice, second electrical stimulation therapy to the patient based onthe input from the patient or the sensor, wherein the delivery of thesecond electrical stimulation therapy generates a second physiologicaleffect that is different than the first physiological effect, andwherein the first and second electrical stimulation therapies areconfigured to manage one of urinary incontinence or fecal incontinence.

In some examples of the method, the first physiological effect comprisesinhibiting contraction of a bladder of the patient, and the secondphysiological effect comprises promoting contraction of one or more of abladder outlet of the patient, an internal urinary sphincter of thepatient, an external urinary sphincter of the patient, or periurethralmuscles of the patient. In addition, in some examples of the method, thefirst electrical stimulation therapy is delivered to the patient on aregular basis and the second electrical stimulation therapy is deliveredto the patient only when the input from the patient or the sensor isindicative of at least one of an imminent involuntary voiding event oran increased possibility of an occurrence of an involuntary voidingevent.

In some examples of the method, delivering the second electricalstimulation therapy comprises delivering a plurality of electricalstimulation signals during a plurality of therapy periods that areseparated by a minimum inter-therapy interval to minimize musclefatigue.

In some examples of the method, delivering the first electricalstimulation therapy comprises delivering the first electricalstimulation therapy to at least one of a pudendal nerve or a sacralnerve, and delivering second electrical stimulation comprises deliveringsecond electrical stimulation to at least one of a hypogastric nerve,the pudendal nerve, the sacral nerve, a dorsal penile nerve, a dorsalclitoral nerve, an external urinary sphincter, or periurethral muscles.

In some examples of the method, delivering the second electricalstimulation therapy comprises delivering the second electricalstimulation therapy for a therapy period of approximately 10 seconds toapproximately 50 seconds.

In some examples of the method, the delivering the second electricalstimulation therapy comprises delivering a stimulation signal comprisingan amplitude of approximately two to approximately four times rheobaseof a target muscle or nerve, a frequency of approximately 15 Hertz toapproximately 66 Hertz, and a pulse width of approximately 100microseconds to approximately 1000 microseconds.

In some examples of the method, delivering the second electricalstimulation therapy comprises delivering the second electricalstimulation therapy according to a first set of stimulation parametersfor a period of time and delivering the second electrical stimulationtherapy according to a second set of stimulation parameters differentthat the first set of stimulation parameters for a subsequent period oftime. In some examples of the method, the first set of stimulationparameters is configured to activate fast-twitch muscles of the patient,and the second set of stimulation parameters is configured to activateslow-twitch muscles of the patient.

In some examples of the method, delivering second electrical stimulationtherapy to the patient based on the input from the patient or the sensorcomprises delivering second electrical stimulation therapy for apredetermined period of time based on the patient input.

In some examples of the method, delivering second electrical stimulationtherapy to the patient based on the input from the patient or the sensorcomprises determining whether the input is indicative of a trigger eventfor the second stimulation therapy, determining whether a number oftrigger events detected within a predetermined interval of time isgreater than or equal to a threshold value, and delivering the secondelectrical stimulation therapy to the patient if the number of triggerevents detected within the predetermined interval of time is not greaterthan or equal to the threshold value. In some examples, the methodfurther comprises generating a patient notification if the number oftrigger events detected within the predetermined interval of time isgreater than or equal to the threshold value.

In some examples of the method, the input from the sensor is indicativeof at least one of bladder contraction or detrusor muscle activity. Insome examples, the input from the sensor comprises at least one of abladder impedance value, a current or voltage amplitude value for asacral or pudendal afferent nerve signal, or an electromyogram for amuscle in a pelvic region of the patient.

In some examples of the method, the input from the sensor is indicativeof patient activity level or patient posture. In addition, in someexamples of the method, the input includes sensor input, and the methodfurther comprises determining whether the input is indicative of atrigger event for the second stimulation therapy, generating a patientnotification that indicates prospective delivery of the secondstimulation therapy if the input is indicative of the trigger event,receiving patient input after generating the patient notification, andsuspending the delivery of the second electrical stimulation therapybased on the patient input.

In some examples of the method, delivering the second electricalstimulation therapy to the patient based on the input from the patientor the sensor comprises determining whether a first input is indicativeof a trigger event for the second stimulation therapy, delivering thesecond electrical stimulation therapy to the patient for a first therapyperiod if the first input is indicative of the trigger event, after thefirst therapy period, receiving a second input from the patient or thesensor, after the first therapy period, determining whether the secondinput is indicative of the trigger event, delivering the secondelectrical stimulation therapy to the patient for a second therapyperiod if the second input is indicative of the trigger event, anddeactivating the second electrical stimulation therapy if the secondinput is not indicative of the trigger event.

In some examples of the method, delivering the second electricalstimulation therapy to the patient based on the input from the patientor the sensor comprises determining whether the second stimulationtherapy was delivered to the patient within an immediately precedingperiod of time, delivering the second electrical stimulation therapy tothe patient if the second stimulation therapy was not delivered to thepatient within the immediately preceding period of time, adjusting thesecond electrical stimulation therapy if the stimulation therapy wasdelivered to the patient within the immediately preceding period oftime, and delivering the adjusted second electrical stimulation therapyto the patient. In some examples, delivering the second electricalstimulation therapy comprises delivering first stimulation pulses for afirst period of time and delivering second stimulation signals having alower frequency than the first stimulation signals for a second periodof time, wherein adjusting the second stimulation therapy comprisesadjusting the duration of one of the first period of time or the secondperiod of time.

In some examples of the method, delivering the second electricalstimulation therapy to the patient comprises gradually increasing ordecreasing a first stimulation parameter value defined by the firstelectrical stimulation therapy to a second stimulation parameter valuedefined by the second electrical stimulation therapy according to apredetermined rate of change or over a predetermined duration of time.

In some examples of the method, the first electrical stimulation therapydefines a first value of a first stimulation parameter and a secondvalue of a second stimulation parameter and the second electricalstimulation therapy defines a third value of the first stimulationparameter and a fourth value of the second stimulation parameter, anddelivering the second electrical stimulation therapy to the patientcomprises instantaneously shifting stimulation delivery from the secondvalue to the fourth value of the second stimulation parameter uponreceiving the input and gradually shifting from the first value to thethird value of the first stimulation parameter value according to apredetermined rate of change or over a predetermined duration of time.

In some examples of the method, the first electrical stimulation therapydefines a first value of a first stimulation parameter and a secondvalue of a second stimulation parameter and the second electricalstimulation therapy defines a third value of the first stimulationparameter and a fourth value of the second stimulation parameter, anddelivering the second electrical stimulation therapy to the patientcomprises gradually shifting from the first value to the third value ofthe first stimulation parameter value according to a first predeterminedrate of change or over a first predetermined duration of time andgradually shifting from the second value to the fourth value of thesecond stimulation parameter value according to a second predeterminedrate of change or over a second predetermined duration of time, whereinthe first and second predetermined rates of change are different and thefirst and second predetermined durations of time are different.

In some examples of the method, the first electrical stimulation therapydefines a first value of a first stimulation parameter and a secondvalue of a second stimulation parameter and the second electricalstimulation therapy defines a third value of the first stimulationparameter and a fourth value of the second stimulation parameter, anddelivering the second electrical stimulation therapy to the patientcomprises gradually transitioning therapy delivery from the first valueto the third value of the first stimulation parameter value andsubsequently gradually transitioning therapy delivery from the secondvalue to the fourth value of the second stimulation parameter value.

In some examples of the method, the method further comprises deliveringa prestimulus before delivering the second stimulation therapy. In someexamples, the prestimulus comprises at least one stimulation pulsecomprising an amplitude of about 0.10 to about 0.50 of an amplitude of astimulation signal defined by the second electrical stimulation therapy.In addition, in some examples, delivering the prestimulus comprisesdelivering the prestimulus about 1 millisecond to about 25 millisecondsbefore delivering the second electrical stimulation therapy.

In some examples of the method, the method further comprises deliveringstimulation to block nerve conduction while delivering the secondelectrical stimulation therapy. In some examples, delivering thestimulation to block nerve conduction comprises delivering a stimulationsignal having a frequency of about 200 Hertz to about 20 kilohertz. Inaddition, in some examples, delivering second electrical stimulationtherapy to the patient comprises delivering the second electricalstimulation therapy to a target nerve, and wherein deliveringstimulation to block nerve conduction comprises delivering stimulationto block conduction of the target nerve.

In some examples of the method, the method further comprises deliveringa third electrical stimulation therapy to minimize discomfort to thepatient while delivering the second electrical stimulation therapy. Insome examples, delivering second electrical stimulation therapy to thepatient comprises delivering the second electrical stimulation therapyto a target nerve and delivering the third electrical stimulationtherapy comprises delivering the third electrical stimulation therapy toa dermatome associated with the target nerve.

In other examples, the disclosure is directed to a computer-readablecomprising instructions that cause a programmable processor to control atherapy delivery module to deliver a first electrical stimulationtherapy to a patient to generate a first physiological effect, receiveinput from the patient or a sensor while the therapy delivery module isdelivering the first electrical stimulation therapy, and control thetherapy delivery module to deliver a second electrical stimulationtherapy to the patient based on the input from the patient or thesensor, wherein the delivery of the second electrical stimulationtherapy generates a second physiological effect that is different thanthe first physiological effect, and wherein the first and secondelectrical stimulation therapies are configured to manage one of urinaryincontinence or fecal incontinence.

The techniques described in this disclosure, including those attributedto programmer 24, IMD 16, or various constituent components, may beimplemented, at least in part, in hardware, software, firmware or anycombination thereof. For example, various aspects of the techniques maybe implemented within one or more processors, including one or moremicroprocessors, DSPs, ASICs, FPGAs, or any other equivalent integratedor discrete logic circuitry, as well as any combinations of suchcomponents, embodied in programmers, such as physician or patientprogrammers, stimulators, image processing devices or other devices. Theterm “processor” or “processing circuitry” may generally refer to any ofthe foregoing logic circuitry, alone or in combination with other logiccircuitry, or any other equivalent circuitry.

Such hardware, software, firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. While the techniques describedherein are primarily described as being performed by processor 50 of IMD16 and/or processor 70 of programmer 24, any one or more parts of thetechniques described herein may be implemented by a processor of one ofIMD 16, programmer 24, or another computing device, alone or incombination with each other.

In addition, any of the described units, modules or components may beimplemented together or separately as discrete but interoperable logicdevices. Depiction of different features as modules or units is intendedto highlight different functional aspects and does not necessarily implythat such modules or units must be realized by separate hardware orsoftware components. Rather, functionality associated with one or moremodules or units may be performed by separate hardware or softwarecomponents, or integrated within common or separate hardware or softwarecomponents.

When implemented in software, the functionality ascribed to the systems,devices and techniques described in this disclosure may be embodied asinstructions on a computer-readable medium such as RAM, ROM, NVRAM,EEPROM, FLASH memory, magnetic data storage media, optical data storagemedia, or the like. The instructions may be executed to support one ormore aspects of the functionality described in this disclosure.

The invention claimed is:
 1. A medical system comprising: a therapydelivery module configured to generate and deliver a first electricalstimulation therapy to a patient to generate a first physiologicaleffect and a second electrical stimulation therapy to the patient togenerate a second physiological effect that is different than the firstphysiological effect, wherein the first physiological effect comprisesinhibiting contraction of a bladder of the patient, and wherein thesecond physiological effect comprises promoting contraction of one ormore of a bladder outlet of the patient, an internal urinary sphincterof the patient, an external urinary sphincter of the patient, orperiurethral muscles of the patient; and a processor configured tocontrol the therapy delivery module to deliver the first electricalstimulation therapy to the patient on a regular basis over a period oftime and control, during the period of time, the therapy delivery moduleto deliver the second electrical stimulation therapy only in response toreceived input, wherein the first and second electrical stimulationtherapies are configured to reduce a likelihood of at least one ofurinary voiding events and fecal voiding events.
 2. The medical systemof claim 1, further comprising a sensor configured to at least one ofsense a patient parameter indicative of a bladder condition or adetrusor muscle activity, or generate a signal indicative of patientactivity or posture, wherein the processor is configured to receive theinput from the sensor.
 3. The medical system of claim 1, furthercomprising a user input mechanism configured to receive input from auser indicative of at least one of an imminent involuntary voiding eventof the patient or an increased possibility of an occurrence of aninvoluntary voiding event of the patient, wherein the processor isconfigured to receive the input from the user input mechanism.
 4. Themedical system of claim 1, wherein the received input is indicative ofat least one of an imminent involuntary voiding event or an increasedpossibility of an occurrence of an involuntary voiding event.
 5. Themedical system of claim 1, wherein the therapy delivery module isconfigured to deliver the second electrical stimulation therapy by atleast delivering a plurality of electrical stimulation signals during aplurality of therapy periods that are separated by a minimuminter-therapy interval to minimize muscle fatigue.
 6. The medical systemof claim 1, wherein the therapy delivery module is configured to deliverthe second electrical stimulation therapy for a therapy period ofapproximately 10 to approximately 50 seconds.
 7. The medical system ofclaim 1, wherein the therapy delivery module is configured to deliverthe second electrical stimulation therapy by at least delivering astimulation signal comprising an amplitude of approximately two toapproximately four times rheobase of a target muscle or nerve, afrequency of approximately 15 Hertz to approximately 66 Hertz, and apulse width of approximately 100 microseconds to approximately 1000microseconds.
 8. The medical system of claim 1, wherein the therapydelivery module is configured to deliver the second electricalstimulation according to a first set of stimulation parameters for aperiod of time and according to a second set of stimulation parametersdifferent than the first set of stimulation parameters for a subsequentperiod of time.
 9. The medical system of claim 8, wherein the first setof stimulation parameters is configured to activate fast-twitch musclesof the patient, and the second set of stimulation parameters isconfigured to activate slow-twitch muscles of the patient.
 10. Themedical system of claim 1, wherein the processor is configured tocontrol the therapy delivery module to deliver the second electricalstimulation therapy to the patient for a predetermined period of timefollowing the received input.
 11. The medical system of claim 1, whereinthe processor configured to control the delivery of the secondelectrical stimulation therapy by the therapy delivery module based onthe received input by at least determining whether the input isindicative of a trigger event for the second electrical stimulationtherapy, determining whether a number of trigger events detected withina predetermined interval of time is greater than or equal to a thresholdvalue, and controlling the therapy delivery module to deliver the secondelectrical stimulation therapy to the patient in response to determiningthe number of trigger events detected within the predetermined intervalof time is not greater than or equal to the threshold value.
 12. Themedical system of claim 11, wherein the processor is configured togenerate a patient notification in response to determining the number oftrigger events detected within the predetermined interval of time isgreater than or equal to the threshold value.
 13. The medical system ofclaim 1, further comprising a sensor configured to generate a signal,wherein the processor is configured to determine whether the signal isindicative of a trigger event for the second electrical stimulationtherapy, generate a patient notification that indicates prospectivedelivery of the second electrical stimulation therapy in response todetermining the signal is indicative of the trigger event, receivepatient input after generating the patient notification, and control thetherapy delivery module to suspend the delivery of the second electricalstimulation therapy upon receiving the patient input.
 14. The medicalsystem of claim 1, wherein the processor is configured to control thetherapy delivery module to deliver the second electrical stimulationtherapy based on received input by at least determining whether a firstreceived input is indicative of a trigger event for the secondelectrical stimulation therapy and controlling the therapy deliverymodule to deliver the second electrical stimulation therapy for a firsttherapy period in response to determining the first received input isindicative of the trigger event, wherein after the first therapy period,the processor is configured to determine whether a second received inputis indicative of the trigger event, the second received input beingreceived after the first received input, control the therapy deliverymodule to deliver the second electrical stimulation therapy to thepatient for a second therapy period in response to determining thesecond received input is indicative of the trigger event, and controlthe therapy delivery module to deactivate the second electricalstimulation therapy in response to determining the second received inputis not indicative of the trigger event.
 15. The medical system of claim1, wherein the processor is configured to control the therapy deliverymodule to deliver the second electrical stimulation therapy based onreceived input by at least determining whether the second electricalstimulation therapy was delivered to the patient within an immediatelypreceding period of time, controlling the therapy delivery module todeliver the second electrical stimulation therapy in response todetermining the second electrical stimulation therapy was not deliveredto the patient within the immediately preceding period of time,adjusting the second electrical stimulation therapy in response todetermining the stimulation therapy was delivered to the patient withinthe immediately preceding period of time, and controlling the therapydelivery module to deliver the adjusted second electrical stimulationtherapy to the patient.
 16. The medical system of claim 15, wherein thesecond electrical stimulation therapy includes first stimulation pulsesand second electrical stimulation pulses having a lower frequency thanthe first stimulation pulses, wherein the processor is configured tocontrol the therapy delivery module to deliver the second electricalstimulation therapy by controlling the therapy delivery module todeliver the first stimulation pulses for a first period of time andcease delivering the first stimulation pulses and deliver the secondelectrical stimulation pulses for a second period of time, and whereinthe processor is configured to adjust the second electrical stimulationtherapy by adjusting at least one of the first period of time or thesecond period of time.
 17. The medical system of claim 1, wherein theprocessor is configured to control the therapy delivery module todeliver the second electrical stimulation therapy to the patient bycontrolling the therapy delivery module to at least gradually increaseor decrease a first stimulation parameter value defined by the firstelectrical stimulation therapy to a second electrical stimulationparameter value defined by the second electrical stimulation therapyaccording to a predetermined rate of change or over a predeterminedduration of time.
 18. The medical system of claim 1, wherein the firstelectrical stimulation therapy defines a first value of a firststimulation parameter and a second value of a second electricalstimulation parameter and the second electrical stimulation therapydefines a third value of the first stimulation parameter and a fourthvalue of the second electrical stimulation parameter, wherein theprocessor is configured to control the therapy delivery module todeliver the second electrical stimulation therapy to the patient bycontrolling the therapy delivery module to at least instantaneouslyshift stimulation delivery from the second value to the fourth value ofthe second electrical stimulation parameter upon receipt of the inputand gradually shift from the first value to the third value of the firststimulation parameter value according to a predetermined rate of changeor over a predetermined duration of time.
 19. The medical system ofclaim 1, wherein the first electrical stimulation therapy defines afirst value of a first stimulation parameter and a second value of asecond electrical stimulation parameter and the second electricalstimulation therapy defines a third value of the first stimulationparameter and a fourth value of the second electrical stimulationparameter, wherein the processor is configured to control the therapydelivery module to deliver the second electrical stimulation therapy tothe patient by controlling the therapy delivery module to at leastgradually shift from the first value to the third value of the firststimulation parameter value according to a first predetermined rate ofchange or over a first predetermined duration of time and graduallyshift from the second value to the fourth value of the second electricalstimulation parameter value according to a second predetermined rate ofchange or over a second predetermined duration of time, wherein thefirst and second predetermined rates of change are different and thefirst and second predetermined durations of time are different.
 20. Themedical system of claim 1, wherein the first electrical stimulationtherapy defines a first value of a first stimulation parameter and asecond value of a second electrical stimulation parameter and the secondelectrical stimulation therapy defines a third value of the firststimulation parameter and a fourth value of the second electricalstimulation parameter, wherein the processor is configured to controlthe therapy delivery module to deliver the second electrical stimulationtherapy to the patient by controlling the therapy delivery module to atleast gradually transition therapy delivery from the first value to thethird value of the first stimulation parameter value and subsequentlygradually transition therapy delivery from the second value to thefourth value of the second electrical stimulation parameter value. 21.The medical system of claim 1, wherein the processor is configured tocontrol the therapy delivery module to deliver a prestimulus beforedelivering the second electrical stimulation therapy.
 22. The medicalsystem of claim 21, wherein the prestimulus comprises at least onestimulation pulse comprising an amplitude of about 0.10 to about 0.50 ofan amplitude of a stimulation signal defined by the second electricalstimulation therapy.
 23. The medical system of claim 21, wherein theprocessor is configured to control the therapy delivery module todeliver the prestimulus about 1 millisecond to about 25 millisecondsbefore delivering the second electrical stimulation therapy.
 24. Themedical system of claim 1, wherein the processor is configured tocontrol the therapy delivery module to deliver stimulation to blocknerve conduction while delivering the second electrical stimulationtherapy.
 25. The medical system of claim 1, wherein the processor isconfigured to control the therapy delivery module to deliver a thirdelectrical stimulation therapy to produce paresthesia while the therapydelivery module delivers the second electrical stimulation therapy. 26.The medical system of claim 1, wherein the therapy delivery modulecomprises a first therapy delivery module, the medical system furthercomprising a second therapy delivery module configured to deliver athird electrical stimulation therapy to the patient to produceparesthesia while the first therapy delivery module delivers the secondelectrical stimulation therapy.
 27. The medical system of claim 1,wherein the first and second electrical stimulation therapies areconfigured to reduce, during delivery of the first and second electricalstimulation therapies to the patient, respectively, a likelihood of atleast one of urinary voiding events and fecal voiding events.
 28. Themedical system of claim 1, wherein the therapy delivery module isconfigured to overlap delivery of the second electrical stimulationtherapy with delivery of the first electrical stimulation.
 29. Themedical system of claim 1, wherein the processor is configured tocontrol the therapy delivery module to deliver the first electricalstimulation during one or more first time slots and deliver the secondelectrical stimulation therapy during one or more second time slotsdifferent than the first time slots.
 30. A method comprising:controlling, by a processor, a therapy module to deliver firstelectrical stimulation therapy to a patient on a regular basis over aperiod of time to generate a first physiological effect; receiving inputfrom the patient or a sensor; and controlling, by the processor andduring the period of time, the therapy module to deliver secondelectrical stimulation therapy to the patient only in response to theinput from the patient or the sensor, wherein the delivery of the secondelectrical stimulation therapy generates a second physiological effectthat is different than the first physiological effect, wherein the firstand second electrical stimulation therapies are configured to reduce alikelihood of at least one of urinary voiding events and fecal voidingevents, wherein the first physiological effect comprises inhibitingcontraction of a bladder of the patient, and wherein the secondphysiological effect comprises promoting contraction of one or more of abladder outlet of the patient, an internal urinary sphincter of thepatient, an external urinary sphincter of the patient, or periurethralmuscles of the patient.
 31. The method of claim 30, wherein the inputfrom the patient or the sensor is indicative of at least one of animminent involuntary voiding event or an increased possibility of anoccurrence of an involuntary voiding event.
 32. The method of claim 30,wherein controlling the therapy module to deliver the second electricalstimulation therapy comprises controlling the therapy module to delivera plurality of electrical stimulation signals during a plurality oftherapy periods that are separated by a minimum inter-therapy intervalto minimize muscle fatigue.
 33. The method of claim 30, whereincontrolling the therapy module to deliver the second electricalstimulation therapy comprises controlling the therapy module to deliverthe second electrical stimulation therapy for a therapy period ofapproximately 10 seconds to approximately 50 seconds.
 34. The method ofclaim 30, wherein controlling the therapy module to deliver the secondelectrical stimulation therapy comprises controlling the therapy moduleto deliver a stimulation signal comprising an amplitude of approximatelytwo to approximately four times rheobase of a target muscle or nerve, afrequency of approximately 15 Hertz to approximately 66 Hertz, and apulse width of approximately 100 microseconds to approximately 1000microseconds.
 35. The method of claim 30, wherein controlling thetherapy module to deliver the second electrical stimulation therapycomprises controlling the therapy module to deliver the secondelectrical stimulation therapy according to a first set of stimulationparameters for a period of time and to deliver the second electricalstimulation therapy according to a second set of stimulation parametersdifferent that the first set of stimulation parameters for a subsequentperiod of time.
 36. The method of claim 35, wherein the first set ofstimulation parameters is configured to activate fast-twitch muscles ofthe patient, and the second set of stimulation parameters is configuredto activate slow-twitch muscles of the patient.
 37. The method of claim30, wherein controlling the therapy module to deliver the secondelectrical stimulation therapy to the patient based on the input fromthe patient or the sensor comprises controlling the therapy module todeliver the second electrical stimulation therapy for a period of timebased on the patient input.
 38. The method of claim 30, whereincontrolling the therapy module to deliver the second electricalstimulation therapy to the patient based on the input from the patientor the sensor comprises: determining whether the input is indicative ofa trigger event for the second electrical stimulation therapy;determining whether a number of trigger events detected within apredetermined interval of time is greater than or equal to a thresholdvalue; and controlling the therapy module to deliver the secondelectrical stimulation therapy to the patient in response to determiningthe number of trigger events detected within the predetermined intervalof time is not greater than or equal to the threshold value.
 39. Themethod of claim 38, further comprising generating a patient notificationin response to determining the number of trigger events detected withinthe predetermined interval of time is greater than or equal to thethreshold value.
 40. The method of claim 30, wherein the methodcomprises receiving input from the sensor, and wherein the sensorgenerates a signal indicative of at least one of bladder contractionactivity, detrusor muscle activity, patient activity level, patientposture, bladder impedance, a sacral or pudendal afferent nerve signalor activity of a muscle in a pelvic region of the patient.
 41. Themethod of claim 30, wherein the input includes sensor input, the methodfurther comprising: determining whether the sensor input is indicativeof a trigger event for the second electrical stimulation therapy;generating a patient notification that indicates prospective delivery ofthe second electrical stimulation therapy in response to determining thesensor input is indicative of the trigger event; receiving patient inputafter generating the patient notification; and suspending the deliveryof the second electrical stimulation therapy based on the patient input.42. The method of claim 30, wherein the input comprises a first input,and controlling the therapy module to deliver the second electricalstimulation therapy to the patient based on the first input from thepatient or the sensor comprises: determining whether the first input isindicative of a trigger event for the second electrical stimulationtherapy; controlling the therapy module to deliver the second electricalstimulation therapy to the patient for a first therapy period inresponse to determining the first input is indicative of the triggerevent; receiving a second input; after the first therapy period,determining whether the second input is indicative of the trigger event;controlling the therapy module to deliver the second electricalstimulation therapy to the patient for a second therapy period inresponse to determining the second input is indicative of the triggerevent; and controlling the therapy module to deactivate the secondelectrical stimulation therapy in response to determining the secondinput is not indicative of the trigger event.
 43. The method of claim30, wherein controlling the therapy module to deliver the secondelectrical stimulation therapy to the patient based on the input fromthe patient or the sensor comprises: determining whether the secondelectrical stimulation therapy was delivered to the patient within animmediately preceding period of time; controlling the therapy module todeliver the second electrical stimulation therapy to the patient inresponse to determining the second electrical stimulation therapy wasnot delivered to the patient within the immediately preceding period oftime; and adjusting the second electrical stimulation therapy andcontrolling the therapy module to deliver the adjusted second electricalstimulation therapy to the patient in response to determining the secondelectrical stimulation therapy was delivered to the patient within theimmediately preceding period of time.
 44. The method of claim 43,wherein controlling the therapy module to deliver the second electricalstimulation therapy comprises controlling the therapy module to deliverfirst stimulation pulses for a first period of time and to deliversecond electrical stimulation signals having a lower frequency than thefirst stimulation signals for a second period of time, wherein adjustingthe second electrical stimulation therapy comprises adjusting theduration of one of the first period of time and the second period oftime.
 45. The method of claim 30, further comprising controlling thetherapy module to deliver a prestimulus before delivering the secondelectrical stimulation therapy.
 46. The method of claim 45, whereincontrolling the therapy module to deliver the prestimulus comprises atleast one of controlling the therapy module to deliver the prestimulusabout 1 millisecond to about 25 milliseconds before delivering thesecond electrical stimulation therapy or delivering at least onestimulation pulse comprising an amplitude of about 0.10 to about 0.50 ofan amplitude of a stimulation signal defined by the second electricalstimulation therapy.
 47. The method of claim 30, further comprisingcontrolling the therapy module to deliver stimulation to block nerveconduction while controlling the therapy module to deliver the secondelectrical stimulation therapy.
 48. The method of claim 47, whereincontrolling the therapy module to deliver the second electricalstimulation therapy to the patient comprises controlling the therapymodule to deliver the second electrical stimulation therapy to a targetnerve, the stimulation to block nerve conduction comprising thestimulation delivered to the target nerve.
 49. The method of claim 30,further comprising controlling the therapy module to deliver a thirdelectrical stimulation therapy to minimize discomfort to the patientwhile delivering the second electrical stimulation therapy.
 50. Themethod of claim 49, wherein controlling the therapy module to deliversecond electrical stimulation therapy to the patient comprisescontrolling the therapy module to deliver the second electricalstimulation therapy to a target nerve and wherein controlling thetherapy module to deliver the third electrical stimulation therapycomprises controlling the therapy module to deliver the third electricalstimulation therapy to a dermatome associated with the target nerve. 51.A medical system comprising: means for generating and delivering firstelectrical stimulation therapy to a patient on a regular basis over aperiod of time to generate a first physiological effect; means forreceiving input from the patient or a sensor; and means for delivering,during the period of time, second electrical stimulation therapy to thepatient to generate a second physiological effect that is different thanthe first physiological effect only in response to the input from thepatient or the sensor, wherein the first and second electricalstimulation therapies are configured to reduce a likelihood of at leastone of urinary voiding events and fecal voiding events, wherein thefirst physiological effect comprises inhibiting contraction of a bladderof the patient, and wherein the second physiological effect comprisespromoting contraction of one or more of a bladder outlet of the patient,an internal urinary sphincter of the patient, an external urinarysphincter of the patient, or periurethral muscles of the patient. 52.The medical system of claim 51, further comprising a therapy deliverymodule that comprises the means for delivering the first electricalstimulation therapy and the means for delivering the second electricalstimulation therapy, the system further comprising a processor thatcontrols the therapy delivery module to at least one of deliver aprestimulus to the patient before delivery of the second electricalstimulation therapy, deliver stimulation to block nerve conductionduring delivery of the second electrical stimulation therapy or delivera third electrical stimulation therapy to produce paresthesia tominimize discomfort to the patient during delivery of the secondelectrical stimulation therapy.
 53. A non-transitory computer-readablemedium comprising instructions that cause a programmable processor to:control a therapy module to deliver first electrical stimulation therapyto a patient on a regular basis over a period of time to generate afirst physiological effect; receive input from a patient or a sensor;and control, during the period of time, the therapy module to deliversecond electrical stimulation therapy to the patient only in response tothe input from the patient or the sensor, wherein the second electricalstimulation therapy is configured to generate a second physiologicaleffect that is different than the first physiological effect, whereinthe first and second electrical stimulation therapies are configured toreduce a likelihood of at least one of urinary voiding events and fecalvoiding events, wherein the first physiological effect comprisesinhibiting contraction of a bladder of the patient, and wherein thesecond physiological effect comprises promoting contraction of one ormore of a bladder outlet of the patient, an internal urinary sphincterof the patient, an external urinary sphincter of the patient, orperiurethral muscles of the patient.
 54. The non-transitorycomputer-readable medium of claim 53, further comprising instructionsthat cause the programmable processor to control the therapy module toat least one of deliver a prestimulus to the patient before delivery ofthe second electrical stimulation therapy, deliver stimulation to blocknerve conduction during delivery of the second electrical stimulationtherapy or deliver a third electrical stimulation therapy to produceparesthesia to minimize discomfort to the patient during delivery of thesecond electrical stimulation therapy.